sailboat solar power calculator

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Estimating Solar Panel Size for Boats

The starting point for a successful solar panel installation is quantifying your requirements. We present here a simple analysis based on the test boat used for our recent report on choosing and installing a solar panel. Some values are from experience, and others are accepted rules of thumb. For more details on choosing and installing a solar panel, see the March 2018 issue of Practical Sailor online.

Energy Balance

Look up the current draw of each piece of equipment (confirm with panel ammeter if available) and estimate the number of hours operated. Record the number and capacity of your batteries, recognizing that you cannot draw below 50% charge without shortening their life, and that you will seldom charge past 85% while away from the dock-as a result, only 35% of nameplate capacity is really useable. Finally, total your charging sources, including engine, wind, and solar. For solar, take the rated wattage x 5 hours/12 = amp-hours while on passage and wattage x 7 hours/12 = amp-hours while at anchor (sails do not shade and the boom can be rigged out to the side). This is far below the rated capacity-sailors in the tropics will do better, and sailors farther north or sailing in the winter more poorly-but this is an accepted starting point.

Estimating Panel Output

How many days can you manage with poor generation? Are you willing to economize during a long cloudy stretch? Will you recharge at a marina or by running the engine periodically? Long-term cruisers appreciate an abundance of power, while the occasional cruisers may be satisfied with less.

Saving Power

Every AH (amp-hour) consumed has a real cost in weight, panels, and dollars. If you can reduce consumption by 50 AH/day you will save a battery (the useable capacity), a 120 watt panel, and perhaps a mounting arch. The cost savings might be $500 and 150 pounds for just a few bulbs.

• Lighting. Switch from incandescent to LED and fluorescent lighting, starting with the lights you use most. We use LEDs and fluorescent for the anchor, salon, and cockpit lights, but since we seldom run at night, we left the running and steaming lights alone. Likewise, the deck light and many task lights remain halogen or incandescent; they are not used enough to matter.
• Go to bed at night and get up with the sun. Big savings in juice and more time to play.
• The gas solenoid is a big user for us; it runs the propane fridge and cabin heater, so it is on for long hours, but we can turn it off at night or go without refrigeration now and then.
• Fans. Run them on low speed and watch the hours. A wind scoop doesn’t use power.
• Instruments. Do you actually need GPS and other instruments full-time on passage? Twenty years ago they didn’t even exist. Balance the sails to minimize the load on the autopilot.

If you’re not sure if it’s time to upgrade or replace your solar panels, the upcoming June 2023 issue offers detailed guidance on evaluating old solar panels and house batteries. If you are upgrading your boat’s electrical system, adding new accessories, or just replacing some wires, our recently updated six-volume ebook Marine Electrical Systems covers everything you need to know about electrical systems–including Batteries, System Installation (including rewiring and lightning protection), Panels, Monitors, Charging, Alternative Energy, and AC Systems.

Power Usage Table

Drew Frye is a frequent contributor to Practical Sailor. He blogs at www.saildelmarva.blogspot.com

RELATED ARTICLES MORE FROM AUTHOR

On watch: this 60-year-old hinckley pilot 35 is also a working girl.

Good subject; article can not be understood by most people.

What people need to know is: I have a x feet sailboat; my boat sits idle y days/week, I live in z area; how many watts will I need most of the time?

What people need to know is; do I have enough places to put the panels, are there panels designed to work well vertically, are flexible panels practical?, etc.

There really isn’t any way to get a realistic daily usage estimate without an amp-hour meter. Do you actually know how many hours per day the fridge compressor runs? They cost a couple hundred and take a couple hours to install.

On my boat, it’s the fridge that is the energy hog. Long ago, I replaced almost all lights (cabin, navigation, and anchor) with LEDs. Cut energy use significantly and worth the money. Newer electronics also have lower draw than very old units. Radars now work at a tenth the prior draw.

Can any readers comment on solar panel output for various mount locations? Bimini, dodger, rotating on stanchions, cabin top What’s best? What’s acceptable?

BTW Boats with a head and galley qualify as second homes and thus are eligible for federal credits for solar panels and batteries bigger than 250 amp-hours. 30% off

After communicating with someone cruising in the Pacific I followed his advice…”Put up as much solar you have room for and you can afford.” With that advice I installed 4x140W (560W) Kyocera panels; 2x140W over the dodger and 2x140W on a new stern arch on my Tayana Vancouver 42. The panels are permanently fixed and I never worry about adjusting them for the best angle. On my roundtrip to Hawaii I never had to start the diesel engine to charge the batteries and I don’t have a genset. I did use the Pacific Cup 2012 Sample Energy Budget as a template and modified it for determining my energy use and highly recommend it. I strongly second the comments about being reasonable in your use of electrical power as it is the easiest and most cost-effective way to manage that requirement…take a very hard look at everything that uses electrical power; do you really need it or use it as much as you do?

I don’t understand the reference to just LA/Flood batteries…

I havev all LiFePo4 both main bank and 12v house and never have any power issues…

I simply maxed out as much as physically possible on my narrow beam 40ft sloop both PV and storage…

A couple items i dont understand. The ‘charging chart’ above has engine charging at 2 amps. This seems very low. Most alternators output in excess of 50 amps. Plus the chart has 2 amps for 5 hrs with a total AH of blank. Also dont understand the ‘solar charging row’. The number just dont jive.

The 2 amps is easy; the example boat had two 9.9 hp outboards that charge 1 amp each. Yes, 2 Amps x 5 hours should have been 10 Ah. Of course, many days the engine does not run.

The refrigeration on the boat in the example was propane, thus no usage.

Additionally, it should be obvious that not all of the items will happen every day. Passage making and at-anchor are different.

Every boat is different. The idea is that by estimating usage, generation, and inventory (batteries) you can better understand your system.

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Choosing the Right Solar Panels for Your Sailboat

For sailors, especially those with smaller sailboats, finding the right solar panel solution can be a challenge. Whether you’re living aboard or planning long cruising trips, running essential equipment like a fridge and electronics requires reliable, efficient power. However, space is at a premium, so you need to choose a solar panel that fits your sailboat's design, offers durability, and provides enough energy to meet your needs.

Why Solar Panels are Ideal for Sailboats

Solar power is an ideal energy source for sailboats, particularly smaller vessels. It’s quiet, renewable, and can be customized to suit different boats and energy requirements. However, with limited deck space, selecting the right solar panels can feel like a balancing act between power output, durability, and available space.

Understanding Your Power Needs

The first step in choosing the right solar panels for your sailboat is understanding your power consumption. You’ll need to calculate how much energy your essential devices consume daily. For most liveaboard sailors, this includes your refrigerator, lights, navigation equipment, and charging stations for electronics. Depending on the equipment you’re running, energy needs typically hover around 2,000 watt-hours per day for a moderate setup.

To meet this energy demand, solar panels are typically rated by their power output in watts (W). A 115W solar panel on an annual average generates about 575 watt-hours per day under normal conditions. We calculate this by multiplying the panel's wattage by 5 (115 watts × 5 hours = 575 Wh). This accounts for the fact that only a fraction of the day will generate peak output due to varying sunlight conditions.

In this case, to generate 2,000 watt-hours per day , you would need approximately four 115W panels (2,000 Wh ÷ 575 Wh per panel ≈ 3.5 panels). If your daily usage rises to 4,000 watt-hours , which can happen with more equipment or multiple people aboard, you would need at least seven 115W panels (4,000 Wh ÷ 575 Wh ≈ 7 panels) to ensure consistent power generation. An example of why we multiply Watts by 5 to get Watt Hours

Space Limitations and Choosing the Right Solar Panels

Space is always a concern on smaller sailboats, so you’ll want to choose solar panels that maximize power without taking up too much room. Look for thin, low-profile panels that won’t interfere with the usability of your deck. Walkable solar panels are a great option for sailors who want to preserve deck space. These panels are designed to be durable and can withstand foot traffic, allowing you to step on them without worrying about damaging them or tripping over raised edges.

Durability is another critical factor. Marine environments are harsh, with exposure to saltwater, sun, and wind. You need a panel that’s built to last. Fiberglass composite panels, like the ones offered by Open Waters Solar, are excellent for these conditions. They’re resistant to cracking and built to handle the demands of life at sea. Read more about microcracking here . 

Dealing with Shading on your Sailboat

Shading is a significant issue on sailboats due to the various structures that create shadows, such as the mast, boom, and rigging. Shade can significantly reduce the performance of a solar panel , so it’s crucial to select panels that have built-in bypass diodes. These diodes help maintain efficiency by allowing the electricity to flow around the shaded areas, ensuring your panels continue to generate power even in partial shade.

Choosing the Right Location for Your Solar Panels

Placement of the solar panels on your sailboat is crucial. Most sailors opt to install panels on the cabin top, bimini, or even on an arch if they have one. Make sure you leave enough room for essential tasks like adjusting sails and moving around the deck.

Consider installing flexible panels that can conform to the curves of your boat’s surfaces. These panels are lightweight, easy to install, and don’t require drilling holes into your deck, which can be a concern for boat owners. Open Waters Solar offers flexible panels that are not only highly efficient but also walkable, making them a perfect choice for smaller boats.

Floating Solar: An Innovative Solution for Small Boats

If space is still an issue, you might consider floating solar panels as a solution. Open Waters Solar offers a 300-watt floating solar array that can be cast behind your boat when it’s anchored. This option is ideal for small to medium sailboats that don’t have the real estate for traditional solar installations. The floating array offers the same high-efficiency power generation without taking up any deck space, making it a practical and innovative option for sailors with space constraints.

Considering Your Battery and Electrical System

When installing solar panels on a sailboat, it’s also important to consider your boat’s battery capacity and electrical system. You’ll need to ensure your setup is compatible with your power needs. We’ll cover choosing the right marine battery in another post, but it's important to plan for enough storage to match your solar generation.

Final Thoughts

Choosing the right solar panels for your sailboat requires careful consideration of your energy needs, space limitations, and environmental conditions. Walkable, thin, and low-profile panels are ideal for preserving deck space while providing the necessary power for long voyages. Durable and efficient panels with bypass diodes are a must-have for any marine environment, especially when shading is a concern.

If space is a limiting factor, consider incorporating a floating solar solution like the one from Open Waters Solar. With the right setup, you can enjoy the freedom of sustainable, quiet energy while cruising the open seas.

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A Guide To Marine Solar Panel Installations

Navigating the world of marine solar panel installations can be daunting. This article aims to simplify the process, providing a step-by-step guide to ensure your boat harnesses the sun’s power efficiently.

I understand the challenges of finding the right solar solution for marine environments, with so many factors to consider, from sizing to installation.

Drawing from extensive research and real-world applications, I’ve distilled the essentials, offering insights into the optimal utilization of solar energy on water.

For all boat enthusiasts and eco-conscious sailors out there, this guide is tailored to your unique needs and passion for sustainable marine adventures.

Just like you, I’ve faced the uncertainties of marine solar installations and, through trials and triumphs, gathered invaluable knowledge I’m eager to share with you.

🎯 Choosing Appropriate Solar Panels

Sizing the appropriate solar panels requires some thought and following the steps below.

Calculate The Electrical Consumption Of Each Device

A boat that uses an electric motor as its primary power source requires a much larger solar panel array (and the balance of the system) than one that doesn’t.

You must inventory every electricity device to calculate the boat’s electrical consumption. The value you are looking to calculate is the system watt requirement. 

If the wattage consumption is not listed on the device, you can calculate it by multiplying the current in amperes (A) by the voltage in volts (V)

Calculate The DAILY Consumption on The Boat

After listing each device’s consumption, you must work out its DAILY consumption. To do this, simply multiply the watts (from this previous step) and multiply this by the number of hours it will run each day.

It will result in a value called watt/hours.

When you have this value, add up each consumer’s “watt/hours” and arrive at a total daily consumption for the boat.

Calculate the Capacity and Number of Solar Panels

As a general rule, and in ideal circumstances, a solar panel’s daily production ranges between 2 to 5 times the advertised capacity (in watts). A 200-watt panel will generate between 400w-1000w (1 kW) daily.

Unfortunately, a boat is not an ideal environment, so optimal production will rarely be achieved.

We recommend sizing the panels with the assumption that they will only produce 1.5 to 2 times the rated capacity (this may vary according to the latitude the boat is sailing on and the sea conditions.)

Assuming the boat consumes 1,000 watts (1kw) per day, we recommend installing panels rated for 500 watts to 750 watts per hour.

Size and Space

Once you have calculated the required capacity, it’s time to go shopping. You can now find out which panels produce the required power and balance these against the space you have available.

As a general rule, the higher the solar panel’s production, the greater the efficiency in terms of space. Instead, buy a few high-production panels as opposed to many smaller units.

🔩 Installation Process

While installing a solar system is not difficult, it must be done extremely carefully. If you have not previously installed a solar system, we strongly recommend employing a professional to do the job.

Not only will the installation be done correctly (hopefully!), but you will also have recourse if there are any problems.

A few precautions should always be taken:

• If a solar panel is exposed to the sun, it produces electricity and should always be treated carefully.
• Always install the solar panels last and keep them covered when installing.
• Always use the correct gauge wire and the proper connectors – failing to do this may result in a fire.
• Always ensure that the correct size fuses are installed in the circuit.
• Label all wiring very clearly (this will be invaluable when you need to work on the system in a few years).
• Draw a full circuit diagram and any notes you may need to remind yourself why aspects of the installation were done in a certain way. Photograph this and store the image on your phone or computer – once again, in a few years, you will be thankful that you did.

🔎 Monitoring and Troubleshooting: System Monitoring 

Most charge controllers and inverters can provide in-depth statistics regarding the system’s electrical production and energy usage.

Most problems with solar systems are caused by incorrectly calculating the needed size of the system.

If you find a problem with the system, you should follow the steps below:

• Check the system statistics and look for the system’s daily production, yield, and consumption.
• If the consumption is higher than you predicted, you can take one of two actions (reduce the number of devices at any one time. The second option is upgrading the system to match the boat’s real-time consumption more accurately.

🎛️ Components of Marine Solar Panel Installation

The parts required for a Marine Solar Panel system are listed below.

Solar Panels

As listed below, three categories of solar panels can be used in a boat:

• A Rigid Marine Solar Panel
• A Semi-Rigid Marine Solar Panel
• Flexible Marine Solar Panel

I’ve written a whole comparison of rigid vs flexible marine solar panels and their applications beyond the scope of this article.

1️⃣ Rigid solar panels are the most efficient in electrical production; however, being rigid means they can only be installed on flat surfaces or frames.

The frames that contain rigid solar panels are normally made from aluminum. Although they will flex slightly, they cannot be bent into shape.

Mounting rigid solar panels can challenge owners because there are generally not enough flat surfaces. To overcome this, many boat owners construct a stand-alone frame over the davits at the stern of the boat.

2️⃣ Semi-rigid panels are less efficient than rigid units. Their benefit is that they can be roughly bent to fit around corners. Flexible panels can be flexed against curved surfaces up to a radius of 30 degrees.

It makes them suitable for mounting on a Bimini shade or a curved deck surface. Some semi-rigid marine solar panels can be walked on , which makes them ideal for mounting on the deck fixed roof.

3️⃣ Fully flexible solar panels are the least efficient of all the types. Their advantage is that they can be molded to the mounting surface’s shape. Check out these market-leading flexible marine solar panels , which could be right up your street.

Charge Controller

There are several anomalies in the current produced by a solar panel:

• The solar panels generate a direct current (DC).
• The current fluctuates as the earth’s position relative to the sun changes during the day.
• On a boat, the current also fluctuates because the boat changes position relative to the sun.
• Cloud cover changes the sun’s effect on the panels.

All this means that it is essential to have a component that can manage the “volatility” of the solar panel’s current production and convert it into a usable power source.

The charge controller ensures that a maximum value charge is generated and does not exceed the limitations of the other components. To do this, they have a capability called Maximum Power Point Tracking (MPPT)

Charge controllers convert the solar panel’s production from DC-DC. It may seem strange, but they essentially convert the volatile DC from the panels into a controlled value required by the batteries.

It means they regulate the charge current into the battery and convert the voltage to match its needs.

A charge controller that is MPPT enabled will produce approximately 30% more current by the system.

The system will also need an inverter if the boat has any electrical consumers that require AC.

This component converts the DC power stored in the battery into a usable AC. 

The Charge Controller and Inverter are housed in many systems as a single unit.

Battery Bank

Batteries are needed to store the solar systems’ energy for later use when the sun is absent. Without an adequate battery system, no electricity would be available overnight or during cloudy overcast conditions.

They are a fundamental part of the solar system. Unfortunately, in terms of efficiency and sustainability, the batteries are the weakest component of the solar system architecture.

• Batteries are heavy because most of the motor’s energy propels the battery!
• Electric boats generally have a shorter range than the equivalent gas-powered boats.
• Batteries cannot be recharged as fast as a gas tank can be filled.
• Marine batteries have a finite lifespan, after which they must be replaced.
• Generally speaking, batteries are the most expensive component of the solar system.

Here is a useful link if you want to dive deeper into the process of charging boat batteries with solar panels .

As a rule of thumb, the grade of wiring used from the solar panels to the charge controller should be as follows.

The correct specification connectors must be used for all connections between the solar panels and the charge controller.

The most commonly used connectors are

Your needs will determine the most suitable. Here is a brilliant article explaining the varying uses.

Mounting Hardware

The mounting hardware will be determined by the equipment being installed. Ensure you follow the manufacturer’s instructions and seal all holes with epoxy to ensure no moisture. 

👍 Benefits of Marine Solar Panel Installation

There are many benefits of solar-powered boats and installing a solar electricity-generating system on your boat. The quantifiable benefits that accrue will depend on the degree to which you convert to solar power. 

Reduced Fuel Consumption

The reduction in fuel consumption is directly proportional to the systems converted to solar energy. The options available include:

• Replacing the battery motor’s alternator (or generator) with solar power 
• Converting the main engine to electric power.

Replacing The Battery Motor’s Generator With Solar Power

Most boats have secondary systems (i.e., unrelated to the boat’s motor) that run off electricity. These tend to use lower-capacity batteries that are recharged when the boat’s gas-powered engine is running.

Examples of these systems include:

• Lighting systems
• Navigation equipment
• The anchor cutlass
• Electric sail trims
• Refrigerators
• Music and video systems

The systems generally consume less power than an electric boat motor. Because of this, a smaller solar system is required to provide power and recharge capability.

Converting The Main Engine To Electric Power

Purchasing inboard and outboard engines that run on electricity instead of fossil fuels (oil and gasoline) is now possible. 

Modern electrically powered motors are becoming more viable, and the efficiencies are continually improving. Electric motors are increasingly being seen as an alternative to gas-powered models.

The following summary lists the motors in the Torqeedo outboard motor range as an example of the range of electric outboards available. 

Torqeedo Outboard Motor Range

The following table lists the range of inboard electric motors available from Elco .

The Elco Inboard Motor Model Range

The Advantages Of An Electric Motor

They offer the following benefits.

• Lower fuel costs 
• Less maintenance
• Quieter running
• More precise speed control

The Disadvantages Of An Electric Motor

While they are becoming increasingly efficient, current electric motor technology still has some drawbacks.

• Electric motors are still more expensive, as per the following:

• Batteries offer less range and take longer to recharge.

Environmentally Friendly

There are obvious environmental benefits to switching to solar power:

• Once installed and running, marine solar power installations are emission-free.
• Solar power systems are virtually silent; they only generate noise from the inverter’s cooling fan.
• When docked, a solar-powered boat has no electrical tethers connected to shore-based power supplies.

The Environmental Disadvantages of Solar Power

The disadvantages include the following:

• Batteries that are most suited to solar installations (Lithium-ion) use metals that are environmentally costly to mine.
• There are serious human rights violations in the mining of Lithium and cobalt.
• Producing solar panels is an extremely environmentally expensive process with substantial emissions.
• The end-of-life disposal of solar panels and batteries is a cause for concern.

Low Maintenance

One of the greatest advantages of solar power is the lack of maintenance that it needs.

Unlike gas-powered generators, there are no moving parts and, therefore, no wear from friction. Once a solar system is installed, it can be left alone, apart from ensuring that the solar panels remain clean.

Most systems allow warnings to be generated if out-of-limits situations occur (low battery, inadequate charge, etc.). In these instances, the user can inspect for the problem and take whatever action is needed.

There are only two circumstances where solar systems are vulnerable.

The Battery Is Discharged To Below The Depth Of Discharge Percentage

Batteries should be discharged within the depth of discharge limit the manufacturer sets. 

These limits are generally 50% (Lead acid batteries and related technologies) and 15% (Lithium-ion batteries).

If the batteries are discharged below these levels, the life expectancy will be reduced. It is normally catered for in the inverter, which will stop drawing current once these levels are reached.

Solar Systems Are Vulnerable To Lighting Damage

The main area of vulnerability is in respect of lightning. The massive electrical surge generated by a lightning strike can fry the solar panels, the wiring, the charge controller, the inverter, and the batteries.

Although the system should have substantial fuses built in, they generally cannot prevent damage caused by a direct hit.

❓ Frequently Asked

How often should marine solar panels be inspected and maintained.

Regular inspection and maintenance are crucial for the optimal performance of marine solar panels. It’s recommended to inspect the panels at least once a month for any dirt, debris, or damage. Clean the panels as needed to ensure they are free from obstructions that could reduce their efficiency. Additionally, check the wiring, connectors, and other components of the system for any signs of wear or damage and address any issues promptly.

Are there any safety precautions to consider when cleaning marine solar panels?

Yes, when cleaning marine solar panels, it’s essential to turn off the system and ensure that the panels are not producing electricity. Use soft cloths or sponges to avoid scratching the panels, and clean with mild soapy water. Avoid using abrasive materials or chemicals that could damage the panels. Ensure that the panels are dry before turning the system back on.

Written by:

I’m the founder and chief editor here at Kite Ship. The electrification of boating is the most exciting thing to happen to the marine industry in a generation! Welcome, and I hope that we can provide the portal you need to dive into the world of electric propulsion and power.

Sailboat Solar Power Calculator

How do you size a solar system for a boat?

To size a solar system for a boat, consider the following steps:

• Calculate daily power consumption: Determine the total watt-hours (Wh) used by all electrical appliances on the boat per day.
• Estimate hours of sunlight: Find the average hours of sunlight available in your sailing area per day.
• Calculate daily solar panel output: Divide the daily power consumption by the average hours of sunlight to get the daily solar panel output required.
• Account for losses: Consider losses due to shading, panel orientation, and inefficiencies.
• Select solar panel wattage: Choose solar panels with the wattage closest to the calculated daily solar panel output.

How much power does a sailboat need?

The power required for a sailboat varies depending on the electrical appliances and systems used on board. Some common power needs include lighting, refrigeration, navigation electronics, and communication devices. To determine the power requirements, add up the wattage ratings of all devices used on the boat and calculate the total daily power consumption in watt-hours (Wh).

What will 400 watts of solar power run?

The power generated by 400 watts of solar panels can vary depending on factors like sunlight hours and efficiency. It could be enough to run basic lighting, small electronics, and charge small devices on a sailboat.

How many solar panels do I need to charge a 100Ah battery?

To calculate the number of solar panels needed to charge a 100Ah battery, you need to consider the wattage and voltage of the solar panels and the charge controller. Divide the daily power consumption (in watt-hours) of the boat by the wattage of the solar panels to get the number of panels needed.

What size solar panel to keep the boat battery charged?

To keep the boat battery charged, consider the average daily power consumption and the average hours of sunlight available. Choose a solar panel (or a combination of panels) with a total wattage output that matches or exceeds the daily power consumption.

How big an inverter do I need on a boat?

The size of the inverter needed on a boat depends on the maximum power requirements of the devices you want to run. Add up the wattage ratings of all devices that might be used simultaneously and choose an inverter that can handle that total wattage plus some headroom for efficiency.

How many amp hours does a sailboat need?

The number of amp-hours a sailboat needs depends on the electrical systems and appliances used on board. Calculate the total amp-hours consumed by all devices in a day and choose a battery bank capacity that exceeds this amount to ensure sufficient power.

What is the average mph of a sailboat?

The average speed of a sailboat can vary widely depending on the type, size, and conditions. It can range from a few knots for a small cruising sailboat to over 20 knots for high-performance racing boats.

How much fuel does a 40-foot sailboat use?

The fuel consumption of a 40-foot sailboat will vary based on engine type, cruising speed, and boat weight. On average, a sailboat might use around 0.5 to 1 gallon of fuel per hour of motor use.

What will 600 watts of solar power run?

600 watts of solar power can run various appliances on a sailboat, including lighting, refrigeration, small electronics, and charging devices.

What can I run with 500 watts of solar power?

500 watts of solar power can run basic lighting, small electronics, charge devices, and power low-energy appliances on a sailboat.

How many batteries will a 400-watt solar panel charge?

The number of batteries a 400-watt solar panel can charge depends on the battery capacity and the solar panel’s daily output. Divide the total daily power consumption (in watt-hours) of the batteries by the daily solar panel output to get the number of panels required.

How long will a 100Ah battery run a fridge?

The runtime of a 100Ah battery running a fridge depends on the fridge’s power consumption and the battery’s depth of discharge. It’s recommended to use a deep-cycle battery and consider a battery bank with more capacity for extended usage.

Can I connect solar panel directly to the battery?

It is not recommended to connect solar panels directly to the battery without a charge controller. A charge controller regulates the charging process, preventing overcharging and optimizing battery health.

How long will a 300W solar panel take to charge a battery?

The time it takes for a 300W solar panel to charge a battery depends on the battery capacity, solar panel output, hours of sunlight, and the efficiency of the charging system.

Will a solar panel charge a deep cycle battery?

Yes, a solar panel can charge a deep cycle battery. A charge controller should be used to regulate the charging process and prevent overcharging.

How much does it cost to add solar to a sailboat?

The cost of adding solar to a sailboat varies depending on the solar panel wattage, quantity, charge controller, installation, and other components. It is essential to get quotes from reputable marine solar providers for an accurate estimate.

How long does it take to charge a marine battery with a solar panel?

The time it takes to charge a marine battery with a solar panel depends on factors such as solar panel output, battery capacity, hours of sunlight, and the charging system’s efficiency.

How long will a marine battery last with an inverter?

The lifespan of a marine battery with an inverter depends on the battery type, depth of discharge, and the number of charge-discharge cycles.

What happens if my inverter is too big?

If the inverter is too big, it may draw more power than needed, leading to inefficiency and potential battery drain.

Is it OK to oversize the inverter?

Slightly oversizing the inverter can be beneficial, as it allows for some headroom and ensures that it can handle peak power demands.

What is a lot of hours for a sailboat engine?

The number of hours on a sailboat engine depends on the engine type, maintenance, and usage. A diesel engine can last thousands of hours with proper care.

How many batteries do I need on a sailboat?

The number of batteries needed on a sailboat depends on power requirements and desired runtime. Consider the daily power consumption and the desired battery bank capacity for sufficient power supply.

How many amps does a sailboat autopilot use?

The amp usage of a sailboat autopilot can vary depending on the autopilot’s make and model. Consult the autopilot’s specifications or manual for its specific amp usage.

Is 20 mph wind too strong for sailing?

A wind speed of 20 mph (17 knots) is considered a moderate breeze and is suitable for sailing. However, it can be challenging for inexperienced sailors or in rough seas.

What is the average speed of a 30-foot sailboat?

The average speed of a 30-foot sailboat can vary depending on conditions, but it is generally around 5 to 7 knots.

What wind speed is too much for sailing?

Wind speeds over 30 mph (26 knots) can be too much for sailing, especially for small sailboats. It may be advisable to reef sails or seek shelter in stronger winds.

Can you sail a 40-foot sailboat alone?

Sailing a 40-foot sailboat alone can be challenging, especially during challenging conditions. It is more common for a sailboat of this size to have a crew or experienced skipper.

What is the most fuel-efficient speed for a boat?

The most fuel-efficient speed for a boat is generally around 8 to 10 knots for most displacement hulls.

How fast can a 40 ft sailboat go?

The speed of a 40-foot sailboat depends on its design and conditions. It can typically achieve speeds of 7 to 10 knots under sail.

How many batteries do I need for an 800-watt solar system?

The number of batteries needed for an 800-watt solar system depends on the battery capacity and desired storage capacity for power usage.

What can 1000 watts of solar power?

1000 watts of solar power can run a variety of appliances and devices on a sailboat, including lighting, refrigeration, small electronics, and charging devices.

What will a 1200-watt solar panel run?

A 1200-watt solar panel can run various electrical appliances and systems on a sailboat, depending on the daily power consumption and the hours of sunlight available.

What will a 2000-watt solar system run?

A 2000-watt solar system can run larger electrical appliances and systems on a sailboat, including more extensive lighting, refrigeration, and small electronic devices.

Can a 500-watt solar panel run a refrigerator?

A 500-watt solar panel might not be sufficient to run a refrigerator continuously, especially if it is a larger model with high power consumption.

What can a 3000-watt solar system run?

A 3000-watt solar system can run multiple high-power appliances and devices on a sailboat, including refrigeration, lighting, electronics, and charging needs.

How long does it take to charge a 200Ah battery with a solar panel?

The time it takes to charge a 200Ah battery with a solar panel depends on the solar panel’s wattage, the available hours of sunlight, and the efficiency of the charging system.

How many solar panels can charge a 12V 200Ah battery?

The number of solar panels needed to charge a 12V 200Ah battery depends on the solar panel wattage, the hours of sunlight, and the battery’s charging requirements.

How long will a 200-watt solar panel take to charge a 100Ah battery?

The time it takes to charge a 100Ah battery with a 200-watt solar panel depends on the hours of sunlight, charging efficiency, and the battery’s state of charge.

How long will a 100Ah lithium battery run an appliance that requires 400W?

To calculate the runtime of a 100Ah lithium battery running a 400W appliance, divide the battery capacity in watt-hours (100Ah * battery voltage) by the appliance power consumption (400W).

How long will the battery last with a 1000W inverter?

The battery’s runtime with a 1000W inverter depends on the battery capacity, depth of discharge, and the total power consumption of devices connected to the inverter.

How long will a 100Ah battery run an RV?

The battery’s runtime in an RV depends on the total power consumption of devices and appliances connected to it and the battery’s capacity.

Do I need an inverter from the solar panel to the battery?

An inverter is not necessary between the solar panel and the battery for charging purposes. However, an inverter is needed to convert DC battery power to AC power for using AC appliances.

What happens if you connect the solar panel before the battery?

If you connect the solar panel directly to the battery without a charge controller, the battery can be overcharged, leading to damage and reduced lifespan.

Do you connect the solar panel or battery first?

Connect the solar panel to the charge controller first, then connect the charge controller to the battery. This ensures proper regulation of charging and prevents overcharging.

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Captain Curran's sailing blog

~ a collection of sailing adventures from Alaska to Cabo

September 2, 2015

How much solar power do i need for my boat, ok, let's get started....

How much solar do I need for my sailboat?

Shakedown cruise, 20 comments:.

You'd be very lucky to get 100 Watts from a 100 Watt panel, especially over 5 hours in a day. The 100 Watts is the maximum under (effectively) lab conditions. It also requires a smart regulator. Of course if you're close to the equator, you will be closer to the theoretical lab conditions.

agreed - partial shadows on the panel can knock the output down also - I went with theoretical conditions based on 5 hours/day of sunlight - and yes a good regulator helps..

Seconded on this point.

also remember to include a fuse on the pos. wire, just upstream of the battery - close to the positive terminal - this is important overload protection

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Best Solar Panels for Boats: Top Picks & Essential Guide

Disclosure: Please be aware that some of the links in this post are affiliate links, and I may receive a commission if you make a purchase using those links. However, I only recommend products or services that I personally use or believe will be valuable to my readers. Affiliate links are a way for me to earn a small commission and keep providing you with high-quality content. If you have any questions or concerns, please feel free to contact me at [email protected] . Thank you for your support!

Solar energy is a fantastic way to power your boat. It’s clean, renewable , and reliable. Plus, it helps reduce your reliance on fossil fuels, making your boating experience more sustainable.

Choosing the right solar panels for your boat is essential. You want panels that are specifically designed for marine use. These panels are built to withstand the harsh conditions on the water and can provide the power you need to make sure your boat stays on course.

When looking for solar panels for your boat, there are a few key factors to consider. You’ll want to think about the size and weight of the panels, as well as their power output. It’s important that they’re efficient, easy to install, and durable enough to hold up to the marine environment.

We spent countless hours researching and testing the best solar panels for boats to help you find the perfect fit for your marine adventures. Our goal is to make sure you have the most reliable and sustainable source of power while out on the water.

How Do Solar Panels for Boats Work?

So you’re into boating and looking for a clean, green energy solution? Solar panels are just the ticket.

Solar panels capture sun-rays and convert them into electricity. This way, we can power our boats using a renewable energy source.

Now, let’s see how they work. Solar panels have cells made up of silicon, which can absorb sunlight . When the sun hits them, electrons in the silicon get excited and move. This creates an electrical current.

So, what can we do with this current?

• Charge a battery bank while you sail
• Run various devices like lights, gadgets, or fridges
• Lower your dependence on shore power and fossil fuels

In fact, solar energy for boats is becoming more popular as clean energy solution for boating . It can help you:

• Reduce fuel costs while cruising
• Become more environmentally friendly
• Enjoy a quieter experience on the water

In short, solar panels for boats harness the power of the sun, offering a sustainable and cost-effective way to keep things running. Plus, you’ll be onboard with the green movement.

Best Solar Panels for Boats

We’ve compiled a list of the best solar panels for marine use from top brands such as SunPower, Renogy, and Eco-Worthy. These high-efficiency solar panels will be perfect for your boat.

Renogy 100W Portable Solar Panel

You should definitely check out this Renogy solar panel for its portability and efficiency.

• Portable and easy to set up
• Highly efficient monocrystalline solar cells
• Waterproof 20A charge controller
• A bit heavy at 26.6 pounds
• May not be suitable for long hikes
• Limited to 12V batteries

The Renogy 100W Portable Solar Panel is perfect for charging your boat’s 12V batteries. It’s a foldable, easy-to-carry solar suitcase that offers flexibility for outdoor and off-grid use. Plus, the setup process is straightforward, saving you time and effort.

This solar panel kit uses grade A+ monocrystalline solar cells, which means remarkable efficiency. The advanced smart PWM technology in the charge controller ensures high charging efficiency and safety. So, your boat’s battery gets charged without any worries.

However, it’s essential to know that this solar suitcase weighs 26.6 pounds. While it is portable and compact, it might not be ideal for long hikes or when weight is a concern. Overall, this Renogy solar panel is a great investment for boaters looking for an efficient and portable solar charging solution.

SunPower 50 Watt Flexible Solar Panel

This solar panel is perfect for boaters seeking efficient, reliable energy from the sun.

• High power output and efficiency
• Easy installation with adhesives or grommets
• Durable and lightweight polymer materials
• May not perform as well as rigid panels long-term
• Possible difficulty with connector disconnection
• Limited flexibility up to 30 degrees

The SunPower 50 Watt Flexible panel stands out with its impressive high efficiency rate of 23.5% . With more power generated in a compact space, it helps reduce your engine usage, offering you a more eco-friendly boating experience.

Trusted by boaters worldwide, the panel is made with SunPower’s Gen II back contact cells and lightweight polymer materials, ensuring both durability and flexibility. Installation is also a breeze, with the option to use adhesives or stainless steel grommets in addition to the provided installation guide.

While the flexible panels are easy to transport and install, keep in mind that they may not have the same long-term performance as a conventional rigid panel. Users have also reported some difficulty disconnecting the cables. Overall, the SunPower 50 Watt Flexible Monocrystalline High Efficiency Solar Panel is a top choice for boat owners seeking dependable and efficient solar power.

Topsolar 20W Solar Panel Kit

This 20W solar panel kit is perfect for keeping your boat’s batteries charged all the time.

• Ideal for off-grid 12V battery systems
• Includes solar charge controller and easy-to-install cables
• Durable construction with tempered glass and aluminum frame
• Limited to 20W output
• No batteries included
• Not suitable for larger power needs

We really enjoyed using the Topsolar 20W solar panel kit while out on our boat. It’s an easy and convenient way to keep your boat’s batteries charged , ensuring you can rely on your boat’s electrical system for longer trips or extended periods without shore power. The kit includes everything you need to start charging right away, and it’s also quite small and light, making it perfect for camping or other outdoor activities.

The included 10A solar charge controller is a nice touch, helping protect your battery from overcharging, overvoltage, and short-circuit issues. Installation is a breeze, with pre-drilled holes on the back of the panel for quick mounting and securing. Remember, though, this kit is limited to 20W output, so it’s best suited for smaller power needs like maintaining a single battery.

One thing we wish the kit came with is batteries. However, it’s simple enough to find compatible batteries elsewhere. All in all, the Topsolar 20W solar panel kit is a great fit for boating enthusiasts looking for an effective, easy-to-use solution to keep their batteries charged. Why not give it a try and let solar power keep you afloat?

Sun Energise 20W Solar Battery Charger

A solid choice for boaters seeking an efficient solar battery charger with smart charging features.

• Built-in MPPT charge controller
• Robust and durable design
• IP65 waterproof and spark-proof
• Might not work well under a significant load
• LED indicator could be more informative
• Some users experienced defects after long-term use

The Sun Energise 20W Solar Battery Charger is an excellent addition to your boating setup. Its built-in MPPT charge controller ensures your batteries receive at least 10%-20% more power than competitors, so you can feel confident relying on solar energy to keep your boat’s batteries charged up.

This solar charger is built to last, featuring a sturdy ABS frame and tempered glass which protect the solar cells from harsh weather conditions. No need to worry about UV damage or high wind and load pressure – this solar charger is designed to handle it all.

However, it’s worth noting that some users experienced issues with the solar charger when using it under a significant load. This might not be the best option for heavy-duty power needs, but for light to moderate use, it’s a fantastic choice. The Sun Energise 20W Solar Battery Charger will keep your boat’s batteries charged and ready to go while providing you with peace of mind knowing that it’s protected from various weather conditions and potential hazards.

SUNER POWER 20W Solar Battery Charger & Maintainer PRO

You should consider buying this for efficient charging and maintaining your boat battery.

• Lightweight and portable
• Intelligent MPPT controller
• Waterproof and durable
• Key needs to be on for cigarette lighter pigtail
• Some LED indicator issues
• May stop working after a few months

The SUNER POWER 20W Solar Battery Charger & Maintainer PRO is perfect for maintaining and charging your boat’s battery. With its lightweight and portable design, you can easily bring it on your boat trips and ensure your battery is always ready.

It features an intelligent MPPT controller, which generates 20%-30% more power than other controllers and protects your battery from overcharging and other potential issues. The charger is built to last, made with high-quality materials and is waterproof to withstand harsh weather conditions.

However, there are a few drawbacks. To charge using the cigarette lighter pigtail, you need to have the key on, which could be inconvenient. Some users have reported issues with the LED indicator lights, and a few cases of the charger stopping working after several months of use. Despite these concerns, this solar charger remains a solid choice for keeping your boat battery in top condition.

DOKIO 160W Portable Solar Panel Kit

This solar panel kit is perfect for boating enthusiasts who want a lightweight, easy-to-use solar power solution.

• Lightweight and foldable
• Works straight out of the box
• Sufficient power output for most applications
• Not as powerful as traditional solar panels
• Optimal conditions needed for maximum output
• May not be suitable for larger power needs

We found the DOKIO solar panel kit to be an excellent choice for boaters who need a compact and portable power source. It’s easy to set up and carry, weighing only 7.28lb, and its foldable design makes storage hassle-free.

You can use it to charge all 12V batteries, making it a versatile power supply for a variety of devices. It also features protection against overcharging, overload, and short-circuit, ensuring safe usage.

However, it’s important to keep in mind that this solar panel’s power output heavily relies on optimal sunlight conditions. It may not be the best choice if you need a more reliable power source or have high energy demands. That being said, for casual usage and emergency situations, the DOKIO 160W portable solar panel kit is a fantastic option for boat owners.

ECO-WORTHY 100W Solar Panels

You’ll love these durable, versatile solar panels for your boat.

• Durable quality
• Versatile usage
• Easy to install
• Lower amperage
• Packaging could be better
• Incomplete project

We recently tried the ECO-WORTHY 100W Solar Panels, and we must say we’re impressed. These 12-volt monocrystalline panels are perfect for various off-grid applications like boats, RVs, and garden setups.

What really caught our attention is their durability. They can withstand high wind and snow loads, thanks to the 3.2mm low iron glass surface. The aluminum alloy frame adds to their sturdiness, making them perfect for boating conditions.

Installation is a breeze with the plug & play designed connectors and pre-drilled holes on the back. Just mount them on your boat, and you’re good to go. Remember, though, they may not have the highest amperage available in the market. However, considering their price, we think they’re a great deal.

Overall, if you’re looking for durable, easy-to-install solar panels for your boat, ECO-WORTHY’s product is a fantastic choice. Just keep in mind that while the packaging might not be the best, they’ve handled shipping well in our experience.

ALLPOWERS SP027 Portable Solar Panel Kit

You’ll love this compact, efficient, and durable solar panel kit for boat trips.

• High efficiency (22%)
• Foldable and portable
• Some concerns about real-world output
• May need additional cables
• Could be too bulky for some

This ALLPOWERS solar panel kit is a top pick for boat owners. With its 100W power and 22% efficiency, it’s perfect for powering your devices on the water.

The foldable design makes it easy to pack and store, so you won’t have to worry about it taking up too much space on your boat. Weighing just 7.9 lbs, you can easily carry it around without breaking a sweat.

In addition to its usability, this solar panel is both waterproof and durable. Its nylon construction and adjustable bracket ensure it can withstand the elements while providing the most effective sunlight.

However, it’s worth noting that some users have reported that the actual output of the solar panel may be lower than expected. Additionally, you might need to purchase extra cables, depending on your device requirements. It’s also a bit bulky when folded, which might be a concern for those with limited storage space.

As for its performance, the customer’s review praises the efficiency and design. They were able to achieve 106 watts in sunny conditions on their test run, while another review confirms the durability and compatibility with the ALLPOWERS 300W Power Station battery unit.

In conclusion, the ALLPOWERS SP027 Portable Solar Panel Kit is a solid choice for boat owners seeking a reliable and efficient source of power on their trips.

Factors to Consider When Choosing Solar Panels for Boats

Power needs:.

First, assess your boat’s energy requirements. Consider all devices you use on board, such as navigation systems, lights, or appliances. Think about whether your boat is used for day trips, long trips, or as a liveaboard, since each scenario has different power demands. Solar power systems for yachts often require more energy than smaller boats, so keep that in mind too.

Panel Types:

There are a few types of solar panels to choose from:

• Rigid vs. flexible panels : Rigid panels are more efficient but harder to install on curved surfaces. Flexible panels work better for curved surfaces but may be less efficient.
• Monocrystalline vs. polycrystalline vs. thin-film panels : Monocrystalline panels are the most efficient, polycrystalline panels have a lower cost, and thin-film panels are lightweight but less efficient.
• Perovskite solar panels : These are an emerging technology with potential for higher efficiency and lower costs in the future.

It’s essential to choose the panel type that best suits your boat and energy needs.

Durability and Weather Resistance:

Boat solar panels must withstand harsh marine conditions, such as salt spray, corrosion, and UV radiation. Ensure the panels you choose are made of high-quality materials designed for marine use. Investing in durable solar panels will help them last longer and perform better in tough conditions.

Size and Weight:

Space is often limited on boats, so it’s crucial to select compact, lightweight panels that fit within your available area. Measure your boat’s available space and compare it to the panel dimensions. Keep in mind, flexible panels can often be mounted on curved surfaces, potentially saving space.

Installation and Maintenance:

Different mounting options for solar panels exist, such as rail mounts, deck mounts, or bimini tops. Choose the best option for your boat, and don’t forget proper installation is key for efficiency. Regular maintenance is also vital, so check for corrosion or dirt buildup and clean your panels whenever needed.

In summary, when selecting solar panels for your boat, consider your power needs, panel types, durability, weather resistance, size, weight, installation, and maintenance requirements. With these factors in mind, you’ll be well on your way to finding the perfect solar panels for your vessel.

Frequently Asked Questions

Why choose solar panels for boats.

Solar panels are a great choice for boats because they’re eco-friendly and cost-effective. With solar power, we reduce our reliance on fossil fuels, save on fuel costs, and enjoy a quieter, more peaceful experience on the water.

What are marine solar panels?

Marine solar panels are designed to withstand the harsher environments on boats, such as saltwater, moisture, and extreme temperatures. These panels are more durable , flexible, and corrosion-resistant than regular solar panels, making them perfect for marine use.

How many watts do I need for boat solar panels?

The wattage you need depends on the electrical devices you’ll be using on your boat. First, calculate the total watt-hours per day that your devices consume. Then, divide that number by the sunlight hours available to determine how many watts of solar panels you need. Remember that it’s better to overestimate than underestimate your needs.

How many solar panels do I need to run a boat?

The number of solar panels required depends on their wattage and your power needs. Once you’ve calculated the wattage needed, divide that by the wattage of the panels you’re considering to determine the number you’ll need. For example, if you need 400 watts and are considering 100-watt panels, you would need four of them.

How much solar power does a boat need?

The amount of solar power your boat needs depends on your usage and the devices you have on board. Consider things like lighting, electronics, appliances, and even heating or cooling systems. Once you’ve calculated your total watt-hours per day, you’ll have a better idea of your boat’s solar power needs.

How to calculate your boat’s solar power needs?

To calculate your boat’s solar power needs, follow these simple steps:

• Make a list of all electrical devices on your boat.
• Determine the power consumption (in watts) for each device.
• Multiply each device’s wattage by the average hours of use per day.
• Add up the daily watt-hours for all devices.
• Divide the total daily watt-hours by the sun hours available.

This will give you an estimate of your boat’s solar power needs.

Which solar panels offer the best performance for marine use?

The best solar panels for marine use are ones specifically designed for boats. Look for panels that are flexible, lightweight, durable, and corrosion-resistant. Monocrystalline solar panels are a top choice as they offer higher efficiency and better performance in low-light conditions compared to polycrystalline options. Always opt for high-quality, reputable brands to ensure maximum reliability and performance.

About the Author  Sunsoaked Solar

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The Boat Galley

making boat life better

How Much Solar Power Do You Need?

Published on October 21, 2015 ; last updated on February 19, 2023 by Carolyn Shearlock

Lately I’ve seen several links on Facebook to various articles on determining how much solar power you need for your boat (or camper, or even a home).

After reading several, I felt compelled to chime in with my two cents. And, as is often the case, my views are a little different from the experts.

Basically, I think all the info about how to compute your electrical demand and calculate how many watts of solar will meet that demand are a great starting point. I just don’t think they are the ending point.

I think that neither calculation can be made with any degree of precision in general and the estimates are even more likely to be wrong if you haven’t yet cruised for more than a week or two at a time or only in a different locale than your long-term cruising plans.

The Demand Side

Typically, these articles tell you to do an energy audit. They say to list every single electrical appliance on your boat, figure out how much each runs per day, look up how much each draws when it’s on, and calculate the total usage in terms of amp-hours.

It’s great in theory.

But it’s virtually impossible to know in advance what you’ll use and for how many hours each day! It’s particularly hard to know before you’ve cruised in a particular area, but even experienced cruisers have a hard time knowing exactly what their usage is.

• There can be considerable variation from one day to the next in general.
• If you cruise to a warmer climate, the refrigerator and fans will run far more than you expect. There’s both the temperature difference and — for the refrigerator — you’ll be drinking far more cold drinks over the course of a day, and every warm drink that has to be chilled increases the load on the refrigerator. Seasonal variations will occur too! It’s not unusual for the refrigerator to run twice as much (or more) when full-time cruising in warm climates than it did on weekends in cooler climates.
• If you have a 12v watermaker, you’ll probably make more water than you expect when it’s hot, both for drinking and for showers.
• Friends may stop by to chat and you end up with more lights on and maybe some music too. Oops, that wasn’t in the energy budget.
• How can you estimate an “average” amount for extra lights to work on an emergency repair?
• Taking photos, posting to a blog or Facebook or even just checking on weather can add quite a bit as cameras, computers, tablets and cell phones all have to be charged.
• And if you’re using an inverter to convert DC to AC power, you can check the AC draw of the appliance, but it’s hard to know just how much will be lost in the conversion. It’s often in the 10-20% range, again meaning that you’ll be using more DC power than you estimated (unless you included the conversion loss in your estimate).
• If you are sailing (motor off) you’ll use more power than at anchor due to instruments, autopilot and radar in addition to all the “normal stuff.”

We’ve also found that what the manufacturer calls an “average draw” for an appliance that cycles (such as a refrigerator) often just doesn’t match what happens in real life. They may say it’ll run 20% of the time . . . but assume that the door isn’t opening, you’re not putting anything warm in, and the temperature is 70 degrees. So they may say it has an average draw of 2 amps, or 48 amp-hours a day.

Then you’re getting into it a dozen or more times a day, putting a dozen warm drinks in, and the temperature outside is 90+. Suddenly it’s running 50% of the time and actually drawing 120 amp-hours a day. That’s a difference of 72 amp-hours between the numbers you used for your energy budget and what your actual need is (NOTE: these numbers are for illustration only and probably don’t reflect your refrigerator usage — in very hot weather we’ve had our refrigerator run 56 minutes out of every hour; in cool spells, it may run only 10 minutes an hour.)

The Solar Output

How much a given wattage of solar panel will actually put out on a given day — or even on average — is equally uncertain. Was it cloudy? Sunny? Did the boat lie so that there were shadows on the panels for part of the day? How many hours of usable sun are there where you are? How clean are the panels? If you’re sailing, your sails are likely to shade one or more of your panels, too.

Again, you can make some general estimates but realize that they are only estimates. And yes, the brand/technology of the panel(s) and the charge controller will play a role in the actual production.

Bottom Line

The bottom line is that until you start cruising in your intended cruising grounds with your setup , it’s impossible to know if it’s adequate or not.

Take us, for example. We put a 345-watt high voltage solar panel with a Kid by Midnite Solar MPPT controller on the boat last spring. At the time, it was more than adequate for our needs even with a watermaker We were fully topped up by 11 AM or noon most days. But we had a propane refrigerator, which we just changed to a 12v model. So our demand has gone up.

But how much has it gone up? We don’t know exactly and it will vary from day to day.

And the question remains: How much solar power do we need?

Well, we think we have enough, but we won’t know for sure until we get back in the water in a couple of weeks and start cruising. I can do all sorts of “how much solar” calculations, but the proof will be in actual use. (And yes, we have a generator as a backup.)

And that’s my main point here — the worksheets can help you estimate your usage and how much solar power you might need, but realize that they are only estimates.

If you don’t already have one, a battery monitor is invaluable for telling you if your batteries are being sufficiently charged and how much power you do have. The battery monitor gives you the real story. Read about battery monitors here .

Another thing to remember: I’ve never met anyone who said they’d put too much solar on their boat.

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Reader Interactions

helen Bell says

October 21, 2015 at 6:33 am

Cpt is working on a lithium battery/solar website that has a load calculator that has lots of variables to help you figure your usuage more accurately. He has included usuage demands for each appliance such as light, medium and heavy. Also a place for you to add other things that are unique to your boat. Like you said, Carolyn, it can’t be totally accurate as our needs change but it is pretty close. And knowing where you will be cruising in advance helps. We have lots of electrical things on our boat that lots of others probably do not have. Cptn designed our whole battery management system on our boat. We have been living aboard for over a year now. We do not use marinas at all. We have 1200Kw of solar,1600Ah of batteries (in two banks) and a 7Kw alternator. No generator.

October 21, 2015 at 6:36 am

Cptns website is a work in progress and any input would be appreciated. Also if there are items you want added please let us know. Thanks Carolyn. Love reading your articles

Dave Skolnick (S/V Auspicious) says

October 21, 2015 at 6:51 am

Helen – I think you need to check your numbers. 1,200 kW (1.2 MW or 1,200,000 W) of solar can’t be right. Similarly I don’t think you have a 7,000 W alternator that would be a 500 A alternator. That would have to be either direct drive or five (or more) belts.

Helen Bell says

October 21, 2015 at 12:44 pm

Sorry you are right. That is 1200 watts of solar but the alternator is indeed 7kw. It puts out 300 amps max at 28v and we use a 1 1/2″ cogged timing belt to drive it. It is brushless DC and when the engine is running at 1600rpm we can still generate more than 200 amps. This allows us to fully charge our lithium batteries very quickly.

Carolyn Shearlock says

October 21, 2015 at 8:55 am

Helen, I think maybe autocorrect got you and changed your solar watts to kilowatts. 1200 watts is still a LOT of solar for a boat!

October 21, 2015 at 12:38 pm

Sorry you are right. That is 1200 watts of solar..we run air con, fridges, freezers microwave, toaster, bread maker to name a few.

October 21, 2015 at 6:47 am

An energy audit is only as good as the person who does it. It is the implementation where many of us fail and your point is well taken. In engineering that is where we add a safety margin. *grin*

Your point is well taken about the difficulty, particularly for people just starting out, in making good estimates of usage.

The very best thing you can do is go sailing for a season and use a battery monitor to regularly track usage. That means some other way of charging, for most of us running the main engine which isn’t all that good for it.

Otherwise you use good engineering practice, make the very best estimates you can, get more experienced counsel, and apply a safety margin. Plan for growth with time.

The magnitude of a safety margin is driven by the confidence in the data and the implications of over specification. Some things (battery capacity or solar output) you really can’t get too big. Others (generator size) too big can be as bad as too small.

For solar I would not be shy. A safety factor of 2 would be a nice start and then see if you can make those panels fit your boat.

You can’t have too much solar or too many batteries. *grin*

ChrisW says

October 21, 2015 at 6:55 am

Well, done.

Having solarized-LED-ed our boat more than five years ago, and being statistics junkies, we were challenged by “amp hour budgeting,” and then we hit on another approach which pares well with yours.

Firmly believing deep cycle batteries should never be discharged more than 50% (and we shoot for no more than 30%), we simply sized our solar array to restore that much charge by mid afternoon the following day.

We assumed a latitude where we would be running the engine the least, since our ICW travel would provide plenty of alternator amps, but our island anchoring wouldn’t.

We double checked this against the budget and found the panel wattage allowed room for usage growth even it good battery management didn’t.

Since taking this approach we have only found it necessary to plug in at a dock for air conditioning during the worst of the summer heat.

Solar is not free energy to start with, but the payback, given Florida and Bahamas electric rate cost avoidance has been 25 months rather than the original estimate of 60 months.– and now its free.

Debbie Bowen Crawford says

October 21, 2015 at 1:44 pm

Doug Crawford

Arion McCartney says

October 21, 2015 at 8:57 am

I have been reading all the solar and wind posts that I come across. I see that everyone uses the rated ah’s for appliances, but those ratings are for normal running, I have not seen where anyone has tried to add in the energy that is used for the start-up of those motors which is much greater than the running energy.

October 21, 2015 at 9:06 am

The start up is momentary and thus is an insignificant percentage of the total draw by an appliance over its total usage.

Jenn Cole says

October 21, 2015 at 5:56 pm

As always, useful advice and gets me thinking more broadly … thanks

Raquel Hernandez says

October 22, 2015 at 1:07 am

Brian Liddy

Vito DeLorenzo says

October 22, 2015 at 3:17 am

I see Alex from SeaTek in marathon FL in the picture

October 22, 2015 at 3:22 am

Alex at SeaTek is now installing lithium ion batteries !!

October 22, 2015 at 6:48 am

We have lithium iron phosphate batteeies (LiFePo4) we’ve been using them for over a year now..they are great

LaMarr Harding says

October 22, 2015 at 8:13 pm

Photovoltaics flat on a Bimini or deck house don’t get the full effect or their rated power.

So the cheaper and more practical for me was just get more panels. I hate to admit that I’ve ran out of room. It’s still safer and more practical than to track the Sun

Chris Tyler says

September 9, 2016 at 11:26 am

Alex Miller

SV SeaGlub says

September 9, 2016 at 11:43 am

Our two cents is get as much solar as you can comfortably fit on the boat. Once installed the energy produced is FREE! Both from a cost and maintenance perspective. This year we increased from 440 watts to 640 watts using the same area on the boat. One other thing to mention about when calculating usage / production is that solar panels will be somewhat less efficient as temperatures rise as you head to lower latitudes.

Bill Jackson says

September 9, 2016 at 12:56 pm

As much as will fit.

Tobias Stricker says

September 9, 2016 at 8:10 am

What you need as installed renewable energy? As much as you can install! That simple.

Cruising boats are today swimming electronic device, just like cars are computer today. The demand is rising continuounsly. And solar panels are not this expensive any more. The limit is the space available to install them.

Cory Nickerson says

September 9, 2016 at 2:28 pm

The big issue for me was the more solar I add the more my energy needs increase. First the coffee maker… then the box fans…then the standalone freezer. Time for another 300 watter

Catherine Gilbert says

September 9, 2016 at 2:32 pm

Excellent and insightful article as usual Carolyn!! We’ve also experienced the impact of heat on the solar panels and therefore producing less than expected, and of course shadowing which is difficult to control as the boat swings on anchor. We added a wind generator as well which is a good pairing for us as it helps many nights with preventing the drain from being quite so deep overnight, allowing the batteries to recover more quickly once the sun comes up in the morning. I think your most salient point is that no-one can tell you how much you really need until YOU get out there living the life – that is the only way to really know how much and what combination of energy retrieval will work for you. Thanks again for a good read!

Gregory Thompson says

September 9, 2016 at 10:21 am

Carolyn, based on your recent trip to the Bahamas, how did you make out solar vs battery and power needs

September 9, 2016 at 1:14 pm

Really well. We ran our Honda generator 3 times and each time was when we had extended cloudy days due to tropical systems. We never used shore power in a marina or bought water.

August 24, 2018 at 10:13 am

Hello, which Honda generator and how did you soften the vibration or mitigate the noise? Gas? I have a dual source gas/propane generator, good choice to go propane and avoid the gas aspect?

August 24, 2018 at 11:45 am

We have the Honda 2000i, which is now the 2200. We just set it on deck. If you use propane, you’ll go through a LOT of it. In many places (such as Bahamas or any remote location) it’s hard to get and expensive. While we don’t really like carrying gas, we do.

SV Coexist says

September 9, 2016 at 3:40 pm

Another great post! Thanks

Sandra Renwick says

September 9, 2016 at 11:46 am

Great information Caroline, what kind of water maker do you have and do you have air conditioning as well that you run on your boat?

September 9, 2016 at 1:16 pm

We have a Katadyn PowerSurvivor 80E — 3.5 gallons per hour, draws 10 amps when running. Most days we ran it for 2 hours. We do not have boat air conditioning (used a portable one last summer when we were on the hard all summer).

September 9, 2016 at 11:48 am

Sorry spelt your name incorrectly, Carolyn.

Laine Common says

September 9, 2016 at 5:45 pm

Nathan Common

Rosalind Franks says

September 9, 2016 at 7:21 pm

John Woodworth

Joshua Thompson says

September 9, 2016 at 10:25 pm

Drew Skelton says

September 9, 2016 at 10:31 pm

570 watts going on.

Dawn Read says

September 10, 2016 at 5:08 pm

Lucky, we were just talking about this this very morning. Check it.

Ronald Harbin says

April 13, 2017 at 4:59 am

Great post – thanks for the reality check. I agree with you 100%. I’ve made spreadsheets and done all the calcs. That’s one main reason why I’m going for a mini (1 to 2 week) cruise on the Chesapeake this summer – to make sure my 165 watts of solar will handle my loads. I’m mostly solo and am pretty conscious of my energy in and out. I’m heading for the Bahamas next winter and have a plan that includes good habits like charging devices only when the engine is running etc.

Warik Hunt says

June 20, 2017 at 11:04 am

I would say the need for solar power will depend on what you’re running and how long you’re running it for. Ie lights fridge freezer computers radios sonar etc etc

SV Pearl Lee says

June 20, 2017 at 11:26 am

Moving our boat from Wisconsin to Florida we ran into one factor we hadn’t considered. Being aboard in winter means shorter days and less production. In our case about a 30% drop. ~ Tom

CJ Grabenstein says

June 20, 2017 at 11:52 am

We added an extra 100w over the winter as this happened to us too!

The Boat Galley says

June 20, 2017 at 12:15 pm

Less production, but also somewhat less usage for fridge and fans. We also run our waterrmaker off 12v (solar) and make more water in summer as we drink more, and rinse off from showering more. Not quite a perfect trade-off, but close.

June 20, 2017 at 3:48 pm

We came up a bit short in December. We’re about to add some more. ~ Tom

Scott Beachbum says

June 20, 2017 at 1:23 pm

Pretty good real life demo on solar issues on the Gone with the Wynns vlog. http://www.gonewiththewynns.com/Sailboat-Solar-Series-Parallel-Shading

June 20, 2017 at 1:55 pm

Good info there, but note that they have one of the biggest arrays I’ve seen on a family boat. We do quite well on 345 watts, all in one panel 🙂 and we run refrig, watermaker and electronic toys as well as fans, lights, pumps, etc.

June 20, 2017 at 2:38 pm

I guess that is the biggest advantage to having a Cat. Lots of space to farm the sun!

Bill McNutt says

June 20, 2017 at 3:53 pm

More, duh. You need MORE.

Doug Treff says

June 20, 2017 at 6:48 pm

It’s like trying to estimate how much money or water you will need for cruising. Everyone makes informed decisions about all these resources… be they money, water, or Amps. Using too much money? Eat out less. Using too much water? Shower less, or get a water maker. Using too many amps? The off some unneeded accessories. Everything is a tradeoff. But generally all the comments are right. I’ve test to hear of anyone who installs TOO MUCH solar.

David Haley says

June 21, 2017 at 2:26 am

you need solar and a Elon Musk Battery.

Garry Rosier says

June 21, 2017 at 6:11 am

I didn’t do any usage estimates. I just installed as much sola as I had space for. Two 320 watt panels, and 440 AH of battery storage. So far so good.

Jennifer Lynch says

November 5, 2020 at 1:22 pm

Newbie here and I’m lookin at a Cat with 1005 W of solar its 47″ foot. I have no idea if this is a normal amount to run everything. I wouldn’t go with ac or modern amenites.

November 20, 2020 at 9:02 am

We have a 34′ boat with 345 watts. I’d say that 1005 is good.

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Solar panel question/Recommendations

• Thread starter artleyt115
• Start date Jan 25, 2023
• Forums for All Owners
• Ask All Sailors

Attachments

• Power plan.pdf 54.7 KB Views: 121

You need to get a charge controller for the solar panel... then... yes... it would be okay to hook it up to your one battery. @Maine Sail has a few good writeups on this topic.  

artleyt115 said: Hello everyone! It’s me again asking more power questions (Hooray!) so I have all my devices in the boat now and I drew up a little excel sheet of how much everything can consume and the hours we plan to run the devices. Now by my (poorly done) math I should expect around 4 day of battery usage of my one GEL 100ah battery with all electronic do-dads on the boat. Now some things (like the fridge) were put at the average consumption, though when I wrote the excel sheet, I put both the initial cooling wattage and the idle wattage (I plan to run that in the house over night before a trip to get the fridge to temp then put it in the boat). So, my questions; if I add another battery in parallel, in theory it should give me 4 days of capacity. If I add another battery, can I put a 200w solar panel on the boat and expect the batteries to be able to take the possible 30amp it can (potentially) produce. And can I put the same solar panel on just one battery for now (Until I buck up and buy the other one) and expect one battery to withstand it? Also (I know sorry) I have a 10a (2 bank) battery charger that I am hooking up, if I get two batteries in parallel can I put one bank on each battery? View attachment 212454 Click to expand

dlochner said: You're off to a good start. If you are unsure of your math, please post the spreadsheet so we can check the formulas, much easier than doing the math ourselves. A few comments: Pick one unit of power, either watt hours or amphours, it is much less confusing that way. Batteries placed in parallel should be of the same age and type to ensure the charges on the battery are balanced. This will lead to longer battery life. Lead Acid batteries generally have a maximum usable capacity of 50% of the total capacity, if the battery is fully recharged between discharges. Realistically, when cruising or when shore power is not accessible, they have a useable capacity of 40%. There are a few exceptions, carbon foam batteries and a couple of high end AGMs have a larger capacity, up to about 70%. Charging a battery is inefficient, it will take between 110% to 120% of the used ah to recharge the battery, i.e., for every 10 ah that is used, recharging will require 12 ah. Solar panels will average efficiencies can be expected to produce 3 times the nominal power each day. A 100 watt panel will produce about 300 watts (25 ah) on average per day, less on cloudy days, a little more on bright sunny days. High efficiency panels (expensive) panels can get close to 4 times. AGM batteries can generally absorb 20 to 40% of their rated capacity when charging in the bulk phase (constant current). This is written as .2C. A 100 ah battery can take a charge of 20 to 40 amps in the bulk phase. Reputable battery manufacturers will use the 20-hour discharge rate to label capacity. Less reputable ones will use the 10 hour rate which tends to yield a higher capacity rating, but less actual capacity in real life settings. A two bank charger can not deliver more than its rated capacity. When 2 batteries are connected, the charge current is divided between the two batteries. Your 10a charger will only put out 5a per battery, which will lead to under charging and very long charge times. Click to expand

dlochner said: You're off to a good start. If you are unsure of your math, please post the spreadsheet so we can check the formulas, much easier than doing the math ourselves. Click to expand

artleyt115 said: This is some really good information, from the sounds of it I should be able to use the 200W solar panel with no issues. (especially with a controller) I'll attach the sheet (though I did not use the formulas on the sheet I just hand did the math) I figured the charger was under powered for even one battery but I mainly figured it was a trickle charger to keep in the boat when I have it on a trailer. Though I didn't know about that absorption rate on the battery, that's awesome! Btw I heard through the grape vine that when a batteries are in parallel they have to be charged slower, is this true? (I don't think this is true but I thought I'd ask) Click to expand

Ralph Johnstone

artleyt115 said: The site wont let me post it :/ Click to expand

artleyt115 said: ... (especially with a controller) ... Click to expand

Timm R Oday25

A couple of thoughts . We also have 25 Oday . A 200 watt solar panel is going to take up an enormous amount of room . We mounted a 30 watt off the back of the rear pulpit . I ran the wiring inside the railing ,under the cockpit and into the regulator mounted on the back of the bulkhead . Most of the electronics you have listed most likely will only run randomly throughout the day . We actually have two solar panels, one for each battery . The "charging" we get from the outboard is maybe 3 to 4 amps . Normally ,we draw down one battery until we are at 12.3 volts . We then flip the battery selector switch to the other battery . While we don't have refrigerator, the auotpilot uses several amps at a time when in use. We've been able to stay out for as long as a week this way  

Timm R Oday25 said: A 200 watt solar panel is going to take up an enormous amount of room . Click to expand

200 Watt 12 Volt Flexible Monocrystalline Solar Panel

Highest Efficiency (up to 25.4%) And Best Flexible, Rigid, And Walkable Marine Solar Panels For Your Boat in 2024. We'll help you decide on the right solar panels to meet your power needs.

Maintenance of Flexible Solar Panels

dlochner said: I didn't realize the site blocked excel files, probably because of macros that could hide malicious code. You must use a controller. The Victron controllers with Bluetooth are a good choice, easy to program and efficient. When batteries are in parallel or series they act as one large battery. Batteries in parallel will increase the ah capacity and the charge capacity will increase, but not the acceptance rate, it will still be .2C, but 20% of 200 ah instead of 100ah. Click to expand

Timm R Oday25 said: A couple of thoughts . We also have 25 Oday . A 200 watt solar panel is going to take up an enormous amount of room . We mounted a 30 watt off the back of the rear pulpit . I ran the wiring inside the railing ,under the cockpit and into the regulator mounted on the back of the bulkhead . Most of the electronics you have listed most likely will only run randomly throughout the day . We actually have two solar panels, one for each battery . The "charging" we get from the outboard is maybe 3 to 4 amps . Normally ,we draw down one battery until we are at 12.3 volts . We then flip the battery selector switch to the other battery . While we don't have refrigerator, the auotpilot uses several amps at a time when in use. We've been able to stay out for as long as a week this way Click to expand

rgranger said: Here are some more ideas and products... Highest Efficiency (up to 25.4%) And Best Flexible, Rigid, And Walkable Marine Solar Panels For Your Boat in 2024. We'll help you decide on the right solar panels to meet your power needs. Marine solar panels with best Sunpower cells, 23.7-25.4%+ efficient, A+ grade solar cells only. All info and consulting available to help you choose the ideal solar panels for your needs. Visit or call, we're more than happy to help. www.custommarineproducts.com Maintenance of Flexible Solar Panels maintenance of your flexible solar panels is easy, simply routinely keep them clean, check for structural integrity, and check the efficiency using monitoring functions in the charge regulators to ensure all is operating at optimum performance. coastalclimatecontrol.com View attachment 212460 View attachment 212461 View attachment 212462 Click to expand

rgranger said: You know.... this rabbit hole is deeeeep! We could start talking about electric outboards, LiFePO4 batteries etc. Click to expand

artleyt115 said: Yea it is, I dont plan to move to LiFEPO4 but I wanted an electric outboard originally just not too many good ones out there yet :/ Click to expand

Cruise – Electric Outboards with 6 to 25 HP – Torqeedo

rgranger said: Actually this Torqeedo Cruise is well reviewed and is equivalent to a 6 HP. My next pocket cruiser will get an upgrade to something like this... Cruise – Electric Outboards with 6 to 25 HP – Torqeedo Torqeedo Cruise outboard motors are state-of-the-art electric drive systems for boats up to 10 tons. With a respectable performance of 6 to 25 HP. www.torqeedo.com I go sailing for the silence and running an OB kind of ruins it for me. Click to expand

I'm confused by the 87w/12w rating on your fridge. You listed 288.0 WH, which is 12w * 24H. 12 watts seems too low. Let's assume 30w on average. Your inverter will draw power, even though you have N/A listed. A Victron Multiplus 2000 will draw anywhere from 3-9 watts depending on how search mode is configured. Let's assume 6 watts draw, 24 hours per day. Your depth meter is only used when sailing, not 24 hours. Call it 6 hours. Using your figures in addition to the assumptions above, I get a total of 3196.2 watts per day. A 200w panel will contribute around 800 watts per day. Figure in losses for voltage drop, battery efficiency and operating with an 80% depth of discharge, you'll need 227 AH of storage or 3 100AH batteries for 1 day away from shore power. Limit the PS4 to a couple of hours per day and you can eliminate 1 battery. But it might cause a mutiny. The numbers seem high but math is math.  

mermike said: I'm confused by the 87w/12w rating on your fridge. You listed 288.0 WH, which is 12w * 24H. 12 watts seems too low. Let's assume 30w on average. Your inverter will draw power, even though you have N/A listed. A Victron Multiplus 2000 will draw anywhere from 3-9 watts depending on how search mode is configured. Let's assume 6 watts draw, 24 hours per day. Your depth meter is only used when sailing, not 24 hours. Call it 6 hours. Using your figures in addition to the assumptions above, I get a total of 3196.2 watts per day. A 200w panel will contribute around 800 watts per day. Figure in losses for voltage drop, battery efficiency and operating with an 80% depth of discharge, you'll need 227 AH of storage or 3 100AH batteries for 1 day away from shore power. Limit the PS4 to a couple of hours per day and you can eliminate 1 battery. But it might cause a mutiny. The numbers seem high but math is math. Click to expand

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Sizing and Selecting Solar Controllers for Boats

With the rising awareness of energy use and conservation, and the expanding demand for power on both day-use recreational and offshore cruising boats, many boat builders and boat owners are turning to alternative sources of power, including solar.  The development of lightweight, marine grade solar panels that can be mounted on canvas, or fully integrated into the decks has made this technology more available to all.  The choice of what panels to install is often straightforward and decided by their size and where/how they can be mounted.  The decision of how to wire the system and choose the best type and number of controllers is more complicated, and is influenced by several factors including – shading and panel configuration; panel voltage, current and wire runs; buck vs. boost controllers; battery type and voltage; temperature sensing capabilities and methods. You need to consider all the variants of the system to make the best choice for a controller.

The sophistication and efficiency of solar controllers has improved greatly in recent years. The MPPT (Maximum Power Point Tracking) controllers have essentially eclipsed the older PWM (Pulse Width Modulation) versions, offering much greater efficiency at harvesting power from the sun.

A quick summary of the differences between PWM and MPPT

The earlier designs of solar panels were made from smaller cells and cut cells put in series, resulting in  voltages that were often higher than was safe for applying directly to a battery for charging.  The PWM (Pulse Width Modulation) solar controllers were developed to keep voltage at a safe charging level.  These controllers feed the power straight to the battery until it reaches a predetermined acceptance level. They then keep the voltage constant and safe by ‘pulsing’ the panel voltage on and off, but this results in significant losses in actual charging current to the battery.

The MPPT (Maximum Power Point Tracking) controllers register the optimal combination of amps and volts in any set of conditions, and then track this ‘power point’ as conditions of light intensity and air temperature change. The DC (direct current) panel output is inverted to high frequency AC (alternating current) and then converted back to DC to charge the battery. The result of this inversion/conversion process is that more amps can be delivered to the battery than were produced by the panel. These controllers are also more efficient in low light angles and soft shading conditions.

This article will focus only on MPPT controllers.

Defining Electrical Terms for Solar Panels 

We will assume the panels have already been chosen. What information do you need about the panels to help you choose the appropriate controller?  All panels are given ratings under Standard Test Conditions (STC). The STC are:  1000 watts per square meter (W/m2) of irradiance; a cell temperature of 25C(77F); and an air mass coefficient of (AM) 1.5.  This is a combination of ideal conditions that will rarely occur, but nevertheless it enables important information to be provided so that cables and fuses can be sized safely.  Depending on the type and number of cells in the panel (cut cell, polycrystalline, monocrystalline), each will put out different amounts of voltage and current (amperage) in varying conditions.

Each rating is defined here:

• Max Power Voltage-Vmp (V) – This is the voltage that occurs when the module is connected to a load and is operating at its peak performance output under standard test conditions (STC). This is determined by the number of cells in series, their basic voltage and the temperature of the cells.
• Max Power Current – Imp (A) – Maximum current the panel will produce when under load. This is dependent on the size, type and quality of the cells, and the strength and quality of the available sunlight.
• Watts – The rated power of a panel under STC. This power rating is equal to the Vmp (max power voltage) X Imp (max power amps). For example, the SP 104 has a Vmp of 18.22v X Imp of 5.71a = 104 watts
• Open Circuit Voltage-Voc (V) – Maximum voltage the panel produces when not connected to a load. Use Voc when calculating voltage limits for series set ups, as this is the maximum possible voltage the panel can put out – even if only for a moment.
• Short Circuit Current Isc (A) – This is the current through a solar cell when the voltage across the solar cell is zero (i.e., when the solar cell is short circuited). Panels built with the same type of cell, will all have the same Isc or short circuit current.

Shading and Panel Wiring Choices

Effects of shading .

Solar panels perform best in bright sunlight at solar noon with little or no shading.  Most boats, either sail or power, will create some type of shade for a solar installation unless the panels are on the very top of a fly-bridge, or extremely far aft on a set of davits or a bimini.

Soft Shading, essentially shadows, will reduce the output of an individual cell if it is completely covered.  Because solar panels are made up of strings of individual cells wired in series, the shaded cell or cells consume power from the non-shaded cells in the series string. Most panels have bypass diodes built into the panels to help alleviate the problem, but often the panel output is reduced by half.

Hard Shading , or when a totally opaque object covers a cell, greatly increases the losses. A hard shadow “…has the effect of knocking out a percentage of the panel’s output equal to the percentage shading of a single cell. ” (Calder, Professional Boatbuilder, #182) Hard shading can also cause the other cells in a string to back feed the covered cell, creating a hot spot, and possibly a fire, so never leave boat cushions or other similar objects on a solar panel!

Some cells are small or cut, and others larger.  The panels made up of smaller cells do poorer in shade, as it is easier to completely cover the individual cells.  Larger, 5 – 6” mono cells are harder to completely cover and therefore do better with soft shading.

Panel Wiring Configurations

Solar panels can be wired three different ways – Isolated, in Series or in Parallel.

Isolated – By far, the best way to manage potential shading of panels is to give each panel its own, individual solar controller.  If a cell on one of the panels is shaded, it only effects the output of that panel, while the other panels continue to function independently.  The drawback to this is the number of wires and controllers to install and manage.

Series – By putting panels in series you essentially create one large panel and this allows you to run a single set of wires down below to a single, larger controller.  This is only recommended when the risk of shading is nonexistent or very low, and wire runs need to be minimized. Only panels with identical cells of equal amperage can be put in series.   Remember the result of putting panels in series is that the voltage of each panel is added together, but the amperage stays the same. This information is important when choosing a controller. For example: Three SR 160 watt panels in series each have a Vmp of 18.6v, but a Voc of 23v.  If they are put in series, the controller needs to be rated for at least 23v x 3 = 69v, not 3 x 18.6 = 55.8v. Also, the total wattage is now 480 watts. However, the Imp 8.6a and the Isc 9a, stays the same. The downside of large series systems is the high DC voltage. Even though the wires size can be relatively small, some builders and boat owners are not comfortable with 60 – 80 volts, DC running through the boat.

Parallel – Panels are sometimes wired in parallel to avoid increasing voltage and to minimize wire runs.  In this situation, blocking diodes must be installed between the panels to prevent a higher producing (non-shaded) panel from back feeding a lower producing (shaded) one.  These blocking diodes also create a voltage drop of approximately 0.7v.  Only identical panels with the same voltage should be put in parallel. The result of paralleling panels is that the voltage stays the same, but the amperage is multiplied.  For example, using the same three SR 160 panels mentioned above, The Vmp and Voc would stay the same but the amperage would be three times that of a single panel, or Imp 8.6a X 3 = 25.8a, total Imp.  This higher amperage creates the need for larger cables to run from the panels to the controllers, and if the run is long, it could be a deterrent to this type of configuration.

Panel Voltage and Current

Buck vs. boost.

As noted above the total voltage and current ratings of panels combined in either series or parallel or even series/parallel combinations vary based on the wiring configuration. All solar controllers are rated to handle differing amounts of voltage, amperage and total watts.  Most controllers bring voltage down to the acceptable charge level (Buck controller), but some raise voltage up (Boost controller).

With the advent of mono crystalline panels, using large cells in small configurations, it is now more common to have a panel that produces less than 12v, but with greater amounts of current.  In fact, most of the more popular panel sizes under 100 watts produce less than the required charging voltage of a 12v battery (13.8v – 14.4v volts). Therefore, it is important to determine whether the output voltage of the panel (or panels) will be greater or less than battery voltage.  If the max power voltage (VMP) is equal to or less than battery voltage, you need a boost controller.  If the voltage is greater than battery voltage, you need a buck controller. At this time, only Genasun and Western make boost controllers. (Western also makes a versatile controller, the WM 10, that will do either buck or boost.) If the panel voltage is over the battery charge voltage of 14.4v, you need a buck controller.

Total Voltage & Watts

Once you have determined whether you need a ‘buck’ or ‘boost’ controller, you next need to compare the total wattage, voltage and amperage ratings of the panel or panels with the ratings of the controller.  For example:  The SR+78 watt panel at 9.6v Vmp requires a boost controller and the Genasun GVB-8-12-Pb has a max panel power rating of 105w. 78 watts is well within the 105 watt rating so you are good to go. The Voc of this panel is only 11.7v, and the controller is rated up to 63v. Finally, if the panel is operating at its maximum power (Vmp) at 9.6v it would be producing 8.1a. The max input current of the GV-B is rated at 8a, but we know from the manufacturer that max current up to 9a is fine.

Now let’s look at a ‘buck’ controller situation. The chosen panel is an SR+ 175 watt, with a Vmp of 21.6v.  A Genasun GV-10 has a limit for max panel voltage (Vmp)  of 34v, so it looks promising; but the rated watts limit is only 140w, and max output current is only 10.5a,  so we need to move to a larger controller such as the Victron 75/15 which has a rating of 200 watts, max panel Voc of 75v and a max output current of 15a. One point of confusion is the difference between the rated current out put of the panel, and the max current output of the controller.  Remembering that the MPPT controllers can actually produce more current than the panel itself. In this case, the SR+ 175 has a Vmp of 21.6v. Since Amps = Watts/Volts — 175/21.6 = 8.1a. So one might think that this panel is OK for the GV 10 since the Voc is fine and it outputs 8.1a.  However, the controller is rated for Max Power Output, and If you divide 175 watts by the battery voltage of 12v you get 14.5a. This output current exceeds the 10.5a rating of the controller.  It is always important to check the total wattage rating of the controller, as this usually will guide you correctly.

When putting panels either in series or parallel, remember to not only add the wattage, but check the total Voc of the panels when in series, and the total Imp of the panels when in parallel.  Suppose we decide to put four SR 108 panels in series on the top of a flybridge where there is no shading. Total wattage – 432w; total Voc – 61.2v; panel output current is 8.6a; but maximum current to a 12v battery bank is (432/12= 36a .) You might think the Victron 100/30 would work as the wattage rating is 440w, the max panel Voc is 100v, BUT- the max output current is only 30a, slightly less than the 36a you need.  Most panels will never quite reach their peak performance, so the 30a might be close enough, but to be safe you need to move up to the 100/50 with the 50a rating.

Putting those same panels in parallel, the total wattage is still 432w, the Voc is now only 15.3v, but the panel current is now 34.4a. (The panel current has a direct effect on the wire size running from the panels to the controller, and for this parallel set up this wire will need to be a much larger diameter, depending on the distance there and back.) The wattage of the parallel set up should still be the primary guide, but again, the power output to a 12v battery system is larger than 30 amps, so always check the max output amps of the controller as well.

Minimum Panel Voltage

Controllers have a minimum voltage to turn on. This important rating is often overlooked.  With the advent of monocrystalline, lower voltage panels, it is important to check for all buck controllers to ensure the panel V is high enough.  Even boost controllers have a minimum amount of voltage needed to turn on, so check the fine print! A GV-10 requires 2V over battery voltage (14v) to function; the Blue Sky only needs 0.2v over battery voltage; the Western requires 2.5v over battery voltage and the Victron needs 5v over battery voltage.

Battery Voltage & Type

Not all battery systems are 12v! Many larger boats are moving to 24v systems, and for electric propulsion, there is a wide range of voltages from 36v, 48v and on up.  Make sure of the voltage of the battery bank that you are going to charge.

Battery Type

The days of flooded lead acid being the only battery type on a boat are long gone. The various types of lead batteries can include – Flooded, Gel, AGM (several variations), TPPL(thin plate, pure lead), Carbon Foam (Firefly), Lead Crystal, etc.,etc. Then there are the increasing Lithium-ion based chemistries.

All of these various types and manufacturers can require different charge parameters. When picking a solar controller for a specific battery type, make sure of what the charge parameters are, and if the stock settings do not suit your battery bank, you will need to find a controller that is fully programmable for the specific needs of your battery chemistry and construction.

Location/Temperature Compensation

Most solar controllers use a form of temperature compensation to moderate the target charge voltages based on battery temperature.  A cold battery can be safely charged at a significantly higher voltage than a warm battery.  Most published charging voltages are for a standard temp of 77 F.  The various controllers get temperature information in different ways.  Some, like the Genasun and original Victron use internal temperature sensing.  This means that they need to be positioned within 12” of the batteries to sense the ambient temperature, or at least be in a compartment that has the same temperature as the battery compartment. Others like the Blue Sky and the Western use a wire that runs from the battery post to the controller.  The newer, “Smart” Victron controllers now use Bluetooth to both send and receive temp and voltage information. They also allow you to view their performance with an app that you can download to your smartphone, tablet or laptop computer.  The simpler controllers either have LED indicator lights to let you know what they are doing or a small readout screen.  What ever controller you choose, it is important to decide where it will be located for viewing or not, and how it gathers the temperature information it needs.

When installing solar panels, you need to estimate the amount of shading. This determines how multiple panels will be wired – either isolated, in series or in parallel. This defines the system voltage and whether you need a buck or a boost controller.  The panel configuration determines the total wattage, voltage and power output that need to be matched to the controller’s ratings. You also need to consider the battery voltage and the type of battery chemistry and charge parameters. Finally, remember the need for temperature compensation, and if/how the controller needs to be read or monitored.

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• Solar on the go

All aboard: How to choose and size solar equipment for your boat

• 14 Mar 2022

Just a while ago a former Navy officer sailed all the way from South Africa to Brazil on a small boat, relying entirely on solar energy. Before you set out to repeat his voyage or make your own route, here is what you need to know about a marine solar installation and how to size it properly.

Talking Size, Shape, Space

Solar panels for boats is a very diverse category. Here you will find flexible thin film panels , small 100W monocrystalline modules and sometimes even larger 300-400W behemoths, depending on the boat’s size. Space is a concern in most cases, so the first two options enjoy more popularity. They help to maximize space by better dealing with uneven surfaces of boats.

You can put panels on a deck, canvas or a stern rail of your boat. Think in advance about the positioning of PV modules: there isn't much unshaded space on board. Solar panels on boats are often shaded by masts or sails and it greatly diminishes their power output.

Number of solar panels depends on your energy consumption

To figure how many panels you need, calculate your daily energy consumption. Write down the power ratings of all the devices and the number of hours in use. Then multiply the power rating and hours for each device. Finally, sum the energy needs of every device together. 

Solar panels perform at their maximum capacity only during peak sun hours. So, once you have the daily energy consumption of your boat, divide it by the number of peak sun hours in your region. What you'll get as a result is the power of the solar array that you need. For more details, check out our detailed guide on calculating solar power needed to travel the seas.

Don't go overboard with solar panels for your boat – you don't need too many, you need just enough. In residential systems , there is always something to do with excess energy from panels: you can sell it to the commercial grid, or even use it to charge your electric car. Out in the open sea you will just throw away that surplus energy. So, with too many panels you may find yourself having spent more money than needed. Plus, extra panels take up space which is really valuable on a boat.

Daily energy consumption × 3 = battery capacity

If your boat doesn't have a house battery yet or you want a new one, think about its size ahead. The amount of your daily energy consumption when on the boat comes in handy here. As a rule of thumb, a house battery capacity should be 3-4 times bigger than your daily energy consumption.

There are several types of batteries on the market, the popular being lithium-ion and lead-acid deep-cycle batteries.

• Lead-acid battery is a traditional choice for a boat battery bank. Its capacity is measured in Amp-hours (Ah). To see if the battery can cover your daily energy needs, multiply Amp-hour by the battery voltage, which is usually 12V. It is not recommended to discharge lead-acid batteries below 50%.

• Lithium-ion batteries rose to glory in the last few years due to the drop in the cost. They are still expensive, but better than lead-acid batteries all around. For example, they handle deep discharge much better, but it is still advised not to discharge it below 20-10% on a regular basis. The capacity of a lithium-ion battery is usually measured in Kilowatt-hours (kWh).

Charge controller protects your house battery

Every solar installation with a battery needs a charge controller, unless you are using very small panels that don't charge your energy storage fully. A charge controller saves your battery from overcharging and deep discharge, and also protects it from high voltage of PV modules. Without a charge controller you risk shortening the lifetime of your house battery.

There are two types of controllers:

• PWM controllers are cheap and reliable, but not very efficient. They only make use of 70-80% of the energy coming from panels. What's more, they work well only in the systems where the voltage of panels is slightly higher than the voltage of a battery. You can get one controller for around $20–$100. Overall, it's a good choice for marine solar panel systems, since they are usually small.

• MPPT controllers are efficient. When the panels' voltage greatly surpasses the one of the battery, an MPPT controller converts that extra voltage into current for the battery. It fits any kind of solar installation and helps use the full power potential of the panels. Their cost, however, can be as high as $1000, and they last a bit less than PWM regulators, from 10 to 15 years.

To size a charge controller for your system, look at its amps size and maximum voltage (VDC). The minimum amps of the controller for your system are the power of your solar array divided by the voltage of the battery. The maximum input voltage is the sum of VOCs (open circuit voltage) of all panels. The open circuit voltage of a panel, as well as the power, is always listed in its specifications.

Add an inverter for AC devices

Not every marine solar system needs an inverter. The lights and even a fridge work fine on the direct current that comes from panels and a battery. But to use a laptop or microwave on a boat, you would need an inverter to turn DC into AC.

The size of an inverter is measured in watts and generally should be close to the power rating of your solar array. For example, if you have three 300W panels, go for a small 1000W inverter. If an inverter is too small, it won't be able to handle the workload and you'll be losing a lot of energy. Check in advance whether your inverter is compatible with the battery's voltage.

Another choice to make is between a pure sine wave inverter and a modified sine wave inverter. The main difference between them is that a modified sine wave inverter is slightly cheaper, but doesn't work with high-tech, precise electronics. For example, you always need a pure sine inverter for modern TVs, electronic clocks and timers. Microwaves and fridges with an AC motor also prefer pure sine wave inverters, while laptops are usually fine with either one.

Why go solar for marine

• Solar panels are silent and smell-less energy generators • Panels are almost maintenance-free and work even when you are away from a boat • Solar panels pay for themselves in 7-8 years on average • PV modules don't need a lot of space and you can put them on a mast, stern rail or even a sail of your boat. Sometimes it's enough to install only one powerful solar panel for the boat battery to get fully charged. • Using renewable energy contributes to fight against global warming

Writing for electronics manufacturers like Bitmain taught Maxim to extract the important details from lengthy equipment documentation. At the same time, it made him aware of the environmental effects, and he put his talents to work for a renewable future.

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Solar Energy

The Ultimate Guide to Solar Panels for Boats

by Federica Rustico 1 year ago 15 min

Reading time 15 min

Boats, irrespective of their size, require a substantial amount of energy for various functions such as maintaining autopilot, illuminating navigation lights, and powering communication systems. Harnessing solar energy for boats is a revolutionary step towards clean, reliable, and cost-effective power. They serve as a dependable power source, ensuring the uninterrupted operation of onboard systems and appliances, from navigation and communication devices to lighting and refrigeration.

They also eliminate the need for carrying additional fuel or relying on marina power hookups, enhancing a boat’s autonomy and reducing operating costs. This way, the journey becomes more enjoyable and less restrictive, whether it’s a leisurely sail or an adventurous long-distance voyage. Adopting solar power for boats also has considerable environmental implications. By leveraging this renewable energy source, we can lower carbon footprints and contribute towards a greener, more sustainable future. Solar panels for boats create no noise pollution, making them the perfect energy solution for maintaining the serene ambiance of marine surroundings. Given these numerous advantages, it’s no surprise that more and more boat owners are equipping their vessels with solar panels. This article provides an in-depth look into the world of marine solar panels and sheds light on why they are an excellent choice for energy generation on your boat.

How Do Solar Panels for Boats Work? 

The operating principle of solar panels for boats is largely similar to their application on land-based systems, with some specific adjustments to cater to the marine environment. At their core, solar panels contain photovoltaic (PV) cells, which are semiconductors that absorb sunlight. This absorbed sunlight triggers the movement of electrons in the semiconductor material, producing an electric current. 

When a solar panel is exposed to sunlight, it produces DC (Direct Current) electricity. However, many boat systems and appliances run on AC (Alternating Current) electricity, which requires the DC electricity to be converted via an inverter. In contrast, some boat-specific equipment, like navigation systems, radios, and certain light fixtures, run directly on DC power. One significant component of a solar power system is the charge controller, or solar regulator, which protects the batteries from overcharging by regulating the voltage and current coming from the solar panels.

Solar panels for boats are often coupled with a battery system for energy storage. The most commonly used batteries are lead-acid and lithium-ion, with the latter becoming increasingly popular due to their longer lifespan, high energy density, and decreasing costs. When sunlight is abundant, the solar panels charge these batteries, storing energy that can be used when the sun isn’t shining or during nighttime operations. In marine applications, solar panels need to be durable to withstand the harsh conditions at sea, including exposure to saltwater, strong winds, and extreme temperatures. Therefore, marine solar panels often come with water-resistant and corrosion-resistant features. They also need to be flexible or semi-flexible to conform to the shape of the vessel and must be installed in a way that does not interfere with the boat’s operations. One significant advantage of solar panels for boats is the potential for an infinite range. When sunlight is available, and the energy system, including battery storage, is well-managed, a solar-powered boat could theoretically operate indefinitely without the need for traditional refueling stops.

Solar Power Suitability for Different Boat Sizes

The application of solar energy transcends the limitations of boat sizes. Regardless of the vessel’s dimensions, incorporating solar power has proven to be an efficient and effective solution. Having enough space on your boat that is unobstructed and exposed to sunlight is crucial for the effective functioning of your solar panels. Shading can drastically reduce energy production. Therefore, it’s essential to identify a suitable spot for permanent installation. For boats with limited space, high-efficiency panels that produce more power per unit area are recommended. To determine the appropriate solar panel setup, you can review the power consumption of your appliances or use a battery monitor to assess your boat’s daily energy consumption. This, in conjunction with the size of your boat’s battery, will guide you in choosing the right solar panels.

Small-sized Boats: For small-sized boats, like dinghies or small sailboats, a limited solar setup can provide ample energy. These boats typically have fewer electronic systems, thus necessitating less power. Small, portable, or flexible solar panels can effectively cater to these energy needs without overwhelming the limited space.

Medium-sized Boats: Medium-sized boats, such as cabin cruisers or larger sailboats, often have more extensive electrical systems, including lighting, refrigeration, navigation equipment, and entertainment systems. They require a more substantial solar setup, often necessitating a combination of portable, flexible, and rigid solar panels to meet their energy demands efficiently.

Large-sized Boats: Large-sized boats like yachts or commercial ships have extensive and varied power needs, including substantial lighting systems, comprehensive navigation and communication equipment, HVAC systems, kitchen appliances, and more. These vessels require a significant investment in solar infrastructure. A combination of high-efficiency rigid solar panels, potentially supplemented with flexible panels to utilize available space, can help meet these higher power demands.

It is important to note that while solar power is a fantastic solution for energy generation on boats of all sizes, the individual needs, space availability, and power requirements should always be considered when designing a boat’s solar energy system.

Do you need a charge controller? 

While installing a solar panel system on your boat, consider incorporating a charge controller. This device ensures your battery is neither overloaded nor overcharged, thereby prolonging its lifespan. Even though it’s not strictly necessary, a charge controller helps your boat use just the right amount of energy and is generally a good idea to install.

Different Types of Solar Panels for Boats

Boating enthusiasts have a wide range of solar panel options to choose from, each with unique benefits and drawbacks. It’s crucial to choose the right one for your boat, taking into account your specific needs, the vessel’s size, and the available space. Here’s a closer look at the three main types: 

Portable Solar Panels

Portable solar panels are growing in popularity among boat owners due to their mobility and easy installation. Their compact design allows for straightforward transportation and setup, making them an excellent option for those seeking a reliable energy source onboard. These solar solutions are not only cost-effective, as they negate the need for fuel, but they’re also maintenance-free and eco-friendly. They produce zero emissions and don’t contribute to noise pollution. When considering portable panels, factors like size, power output rating, and panel quality are critical. It’s equally important to ensure they are waterproof and weather-resistant — panels with an IP68 rating are ideal. Portable panels are an exemplary choice for boaters wanting to keep their ecological footprint minimal while maintaining a steady power supply.

Rigid Solar Panels

Rigid solar panels provide a long-term solution for those wanting a steady power supply for their boat. These are permanently affixed to the boat’s surface and usually composed of robust materials such as tempered glass or aluminum, making them durable. Rigid panels are prized for their efficiency, generating a higher power yield per square inch than portable alternatives. This makes them well-suited for larger vessels or boats with substantial energy needs. Their durability is another significant benefit. These panels can withstand harsh marine conditions, including constant saltwater exposure and extreme weather. However, it’s crucial to ensure that the selected panels are waterproof, with an IP68 rating being optimal. Installation can be complex due to the permanent nature of these panels. Proper mounting is vital to prevent potential damage or loss. Despite this complexity, rigid panels offer room for customization and expansion, as you can form larger arrays by connecting several panels.

Flexible Solar Panels

Flexible solar panels, a recent innovation in solar technology , offer a more adaptable alternative to rigid panels. These consist of lightweight and bendable materials, such as thin-film photovoltaic cells, allowing them to conform to curved or uneven surfaces. The primary advantage of flexible panels is their adaptability. They can fit onto a variety of surfaces, making them an ideal choice for boats, recreational vehicles, and other outdoor applications. Their lightweight design is beneficial where weight restrictions apply.

Flexible panels are also quite durable, capable of enduring severe weather conditions such as hail, rain, and high winds. As with other types, an IP68 waterproof rating is crucial. However, flexible panels do have their drawbacks. They typically generate less power than rigid panels, which can limit their ability to meet high energy demands. They also tend to have shorter lifespans and may need replacing more frequently. In conclusion, flexible panels are best suited for enhancing a rigid solar panel system, allowing you to utilize all available space for solar power generation. They are not intended to be the sole solar solution.

Choosing the Appropriate Solar Panel for Your Boat

The process of choosing the right solar panel for your boat entails several considerations, each essential in ensuring an optimal and efficient solar energy system. Here are the key factors to take into account:

Power Output: First, it’s essential to identify the total energy required by all electrical equipment aboard your boat. This can be achieved by estimating each device’s wattage and operational duration. Following this, calculate the minimum panel output needed to cater to this energy demand by dividing the total watt-hours required by the average number of sunlight hours per day.  The power output also influences the choice of your solar battery and system balance since the overall solar power system must be compatible with your photovoltaic (PV) panels. Note that you cannot feed electricity directly from the panels into your boat appliances; a portable power station or a similar solution is needed to store and distribute the energy. 

Durability and Weather Resistance: It’s crucial to ensure your chosen solar panels are resistant to impact and adverse weather conditions. An IP68 waterproof rating is highly recommended to protect your panels from wave splashes and rainfall.

Size and Weight: The dimensions and weight of the panels should correspond to your energy needs and the available space on your boat. Aim to choose panels that can meet your energy demands without occupying too much space or adding significant weight.

Installation and Maintenance: Consider the time and cost required for installation and maintenance. Depending on the complexity, you might need professional assistance for installation. Note that not all panels require mounting brackets; portable panels allow for flexibility and cost-saving, bypassing the need for permanent installation.

Brand Reputation: It’s advisable to invest in solar panels from a trusted brand with a proven track record of quality and reliability. Seeking reviews and insights from other boat owners can be beneficial when making your decision.

Cost: Solar panel costs can vary based on size, efficiency, and brand. Keep your budget in mind and aim to select panels that offer the best return on investment.

Top Picks for Solar Panels for Boats

When choosing the perfect solar panel for your boat, several factors should be considered, such as efficiency, cost, ease of installation, and durability. Here, we delve into five top-notch solar panels for boats based on EcoWatch :

1. SunPower 170W Solar Panel

Known for their excellent residential solar panels, SunPower extends their reputation into marine applications with their high-performance 170W solar panel. This unit comes at a higher cost, but its robust power output justifies the price. With this panel, you can comfortably power your boat’s primary battery, emergency backups, and various appliances. Unfortunately, this package doesn’t include a solar charge controller or an inverter, necessitating extra expenses. Nevertheless, the power efficiency makes the investment worthwhile. The panel carries an IP67 waterproof rating, enabling it to survive water immersion up to three feet for about half an hour.

• High-quality materials with optimal power output
• Reliable brand reputation
• Waterproof to a depth of about one meter for 30 minutes
• High cost and no extra equipment included

2. Renogy 100W Flexible Marine Solar Panel

For a reasonable cost, the Renogy Flexible solar panel offers respectable power output and waterproofing. With a capacity of 100W, it’s an excellent choice for moderate power needs, charging various electronic devices. It also includes a controller and wiring, only requiring an inverter and battery to complete the setup.

• Good power output with an IP67 waterproof rating
• Comes with a controller and wiring
• Renowned brand
• It costs more than some other options and doesn’t include a battery or inverter

3. EcoWorthy 25W Solar Panel Kit

For those new to solar energy, the EcoWorthy solar panel kit makes a great entry point. The kit includes MC4 connectors, making installation quick and hassle-free. However, its smaller power output restricts its use to backup power or charging smaller electronics. With an IP65 rating, it can endure water submersion up to five feet for half an hour.

• IP65 waterproof rating
• Highly affordable
• No included battery or inverter
• Lower power output compared to top picks

4. NewPowa 30W Solar Panel Kit

The NewPowa solar panel kit is a cost-effective option that includes a panel, a controller, and wiring. With a 30W output, it’s well-suited for light-duty use. Its IP67-rated panels and controller make it a safe choice for various boat types.

• Affordable with an IP67 waterproof rating
• Easy installation
• Low power output
• Battery and inverter not included

5. TopSolar Monocrystalline Solar Panel Kit

If you’re a beginner seeking a backup energy source, the TopSolar kit is an excellent choice. While its 20W output limits its use to emergency power, it’s easy to install and comes at a lower price. Though no specific IP rating is provided, the manufacturer claims it is waterproof.

• Affordable and easy to install
• Includes a controller and wiring
• Suitable for backup power
• Doesn’t include a battery or inverter
• No specific IP rating
• Limited power output

The Benefits of Installing Solar Panels for Boats

Opting to install solar panels on your boat opens a gateway into the realm of clean energy, significantly improving your boating experience in multiple ways. There are a few key use cases that help illustrate the value of adopting a solar panel system on your boat. These scenarios do not only help determine the necessity of solar panels for your vessel, but they also aid in identifying the most suitable and cost-efficient system for your needs. Below, we delve into the different motivations for embracing solar power on your boat.

Emergency Equipment Charging

The unpredictable nature of sea adventures underscores the importance of having reliable emergency equipment on board. Whether you find yourself in a situation where you’ve run out of fuel, encountered a mechanical issue, or faced with other unforeseen complications preventing a safe return to shore, having a dependable communication device can be a lifesaver. Many boats are equipped with emergency systems such as radio systems, satellite phones, or regular phones. However, these devices are reliant on power. By integrating a solar system into your boat, you can ensure a continuous power supply for these devices, providing peace of mind during your sea excursions.

Recreational Equipment Charging

Beyond emergencies, the utility of solar panels extends to everyday recreational needs. Having the ability to charge devices like smartphones, e-readers, speakers, and other entertainment equipment can enhance your sea experience. This aspect gains significance, especially if you plan on spending multiple days at sea and don’t want to deplete your boat’s batteries. By allowing your solar system to handle the power needs of your recreational equipment, you ensure that your boat’s batteries remain sufficiently charged for critical functions such as lighting, navigation tools, and starting your boat’s engine.

Low Maintenance

Solar systems for boats are generally hassle-free once installed, requiring only periodic maintenance to ensure safety and optimal energy production. Approximately every six months, it’s advisable to clean your solar panels by rinsing them with water to remove any accumulation of dirt or salt. This simple routine helps maintain the panels’ efficiency by maximizing energy generation. During these semiannual checks, it’s also crucial to inspect the system’s wires and connectors for signs of corrosion, especially if your boat operates in saltwater environments. Checking for intact connections after major storms is a prudent practice to avoid battery charging issues, which could pose a problem if backup power is ever needed. Solar systems on boats are generally considered safe. There is a minimal risk of fire, but regular maintenance and system checks can effectively mitigate such risks. Therefore, while the maintenance required is not extensive, its impact on safety and efficiency is significant.

Wrapping Up

Installing solar panels on your boat presents an array of benefits that enhance your boating experience while also contributing to the preservation of our planet. From powering emergency and recreational equipment, improving your quality of life at sea, offering a low-maintenance energy solution, to providing silent operation, the advantages of solar power on the water are undeniable. Choosing the right solar panels for your boat might require some careful consideration and calculations, but the payoff in terms of cost savings, environmental impact, and overall comfort is certainly worth the investment. With the advancements in solar technology and growing awareness of sustainable practices, it’s an opportune time to harness the power of the sun and sail towards a greener future.

Frequently Asked Questions:

Do i need a charge controller for my boat’s solar panel system.

While not strictly necessary, a charge controller helps regulate the voltage and current coming from the solar panels, protecting the batteries from overcharging and prolonging their lifespan.

Do solar panels require regular maintenance on boats?

Solar panels on boats require minimal maintenance. Periodic cleaning to remove dirt, salt, or debris and checking connections for any signs of damage or corrosion are recommended to ensure optimal performance.

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