How Much Solar Is Needed For A Boat?
There is no cut-and-dry answer to this question because so many factors and variables must be considered. Along with a plethora of numbers, letters, and equations
This may make this seem beyond a non-mathematical enthusiast’s grasp. Still, it can be pretty simple to calculate how much (and how much of what) you’ll need. So there is no better time to go green!
I’ll cover the numerous aspects that need to be considered to yield an accurate answer so you can charge your boat batteries with solar.
Systems On A Boat Requiring Power
Your boat will require some power, no matter what shape or size. Larger vessels cannot rely on just the wind for sailing and have engines to aid this. These days many ships (especially the bigger ones) have other appliances on board that require power.
When calculating how much solar power is needed for your boat to function, you should compile a list of all the appliances (and their power usage) you have on your boat. Then, when you have added the totals, you will know precisely how much solar power you require.
Unlike standard engines on most boats, vessels that use an electric outboard motor do not require the input of gasoline and can supplement their power from solar fittings.
The output of a solar-powered engine will be lower than that of a vessel powered by gasoline meaning your boat will be slower.
Specialized electric motors need to be fitted to boats for this purpose.
The battery is what is going to be powering all your electronics as well as your outboard. A dedicated battery will provide the motor with the power, and a house battery will be responsible for all other electronics. The size of your battery will depend on the following:
The battery already fitted to your boat can be used if it is a marine deep-cycle battery. But a specialty battery is recommended for all your solar fixtures.
Marine lithium batteries are the best options for your solar power for the following reasons:
Lithium marine batteries may have a high initial cost, but they will be cost-effective over time. Here are some brand comparisons to consider.
Systems like your GPS are essential when out on the water and must be operational at all times. Your VHF marine radio will also need to be connected to the boat’s battery, many of which have GPS built into them.
Power Needed To Maintain Appliances
Once you have an idea of which appliances need to be supplied with power (and for how long), you can calculate your total power needs per day using the following formula:
| Appliance | Power (watts) | Hours of use per day | Power consumption per day in Watt Hours (Wh) | Amperage (A) | Amps per day (Ah) |
|---|---|---|---|---|---|
| Laptop | 50 | 10 | 500 Wh | 4.16 | 41.6 |
| Lights | 20 | 6 | 120 Wh | 1.6 | 9.6 |
| GPS | 30 | 10 | 300 Wh | 2.5 | 25 |
| Fridge | 15 | 24 | 360 Wh | 1.25 | 30 |
| Microwave | 700 | 1 | 700 Wh | 58.3 | 58.3 |
| Total (Wh) | 1 980 Wh | 67.81 A | 164.5 Ah |
Solar Set-Up Scenario
A 25 ft. pontoon will only require power for the motor, GPS, and lights (if that). Surplus appliances, such as fridges, won’t usually be found on these boats. Therefore your solar power will be able to run your vessel for longer.
When looking at the design of a pontoon, the best place for mounting a solar panel system would be at the stern and preferably with an angled mount. It will resemble a spoiler on the back of a sports car.
Specifications Of Our 25 ft Pontoon Boat
| Boat Type | Length Overall | Systems Requiring Power |
| Pontoon Cruiser | 25 feet | Motor; Lights; Navigational System |
Solar Equipment Required For Solar Power Set-Up:
Step By Step Guide: Setting Up Solar Power On A 25 ft. Pontoon
I’ve written a detailed guide to marine solar panel installation which I’d suggest you read. To recap though here are steps and a tutorial video below.
- Select panel size, mounting bracket, and location of where you want it mounted
- Install mounting brackets with relevant openings for solar cabling
- Secure solar panels to mounting brackets
- Run solar cabling
- Connect solar cabling to the charge controller
- Linkup the charge controller to the battery bank
- Connect the battery bank to the converter
- Connect the converter to the motor, lights, and GPS system.
- Charge solar panels in the sun
Since a pontoon boat of this size won’t require additional power for appliances, a portable solar panel could be used. But the panel might only be enough to power the battery.
Estimate for solar power needed on a 25 ft pontoon:
| System | Power (watts) | Hours of use per day | Power consumption per day |
| Engine | 85 | 8 | 680 Wh |
| Lights | 20 | 6 | 120 Wh |
| GPS | 30 | 8 | 300 Wh |
| Total (Wh) | 1100 Wh |
🎖️ Pro Tip: If you opt for flexible panels over rigid panels you can benefit from increased surface areas to produce more power.
Solar Power And Electric Propulsion
Many types of boats can be fitted with an electric motor, such as sailboats, jon boats, center consoles, catamarans, etc.
Sailboats vs Electric Propulsion Boats
Electric propulsion boats, like these Silent Yachts, rely almost entirely on solar power. Therefore, in comparison to standard diesel-powered sailboats, electric propulsion vessels are more eco-friendly.
They will be the most cost-effective in the long run. However, the initial expense for a Silent Yacht or equivalent vessel will be high.
Boats whose propulsions are entirely solar-powered will not be known for speed. But advancements are being made every day, and soon we could see an eco-friendly solar-powered vessel with impressive speeds.
| Sailboats | Electric Propulsion Boats |
|---|---|
| Require a hands-on approach | Easier to operate |
| More training and practice required | Require less experience |
| Save money on fuel; maintenance more frequent but cheaper overall | More costly to maintain; less maintenance overall |
| Many moving parts | Fewer components |
| More reliant on favorable conditions; at the mercy of the winds | More space on board for other purposes |
| Tides and sail setup crucial in certain conditions | Quieter, fewer fumes and vibrations |
