How Much Solar Is Needed For A Boat?

There is no cut-and-dry answer to this question. This is because so many factors and variables need to be considered.

But don’t worry, I’ve got you. When researching solar power and solar panels for all things marine orientated, you may need clarification on the 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.

Even if it isn’t simple, there are ways of calculating these things online. So there is no better time to go green!

I have covered numerous aspects that need to be considered to yield an accurate answer.

⚙️ Which Systems On A Boat Require 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.

The Engine

Unlike standard engines on most boats, vessels that use an electric motor do not require the input of marine gasoline but get their power from solar fittings.

The output of a solar-powered engine will be lower than that of a vessel powered by gasoline. This means that your boat will be slower. Specialized electric motors need to be fitted to boats for this purpose.

Batteries

The battery is what is going to be powering all your electronics as well as your engine. A dedicated battery will provide the engine with the power, and a house battery will be responsible for all other electronics. The size of your battery will depend on the following:

1️⃣ The size of your engine
2️⃣ The voltage of your motor
3️⃣ Maximum amp draw of your motor
4️⃣ The number of electronics on board that require power

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. Batteries like marine lithium batteries are the best options for your solar power for the following reasons:

• Superior energy storing for solar systems
• Faster charger
• Longer lasting
• No maintenance is required
• Longer lifespan

Lithium marine batteries may have a high initial cost, but they will be cost-effective over time.

The Dakota Lithium Batteries site offers a comprehensive breakdown of how to go about calculating the required size of a battery relative to your boat. As well as a guide on choosing the best battery for your trolling motor.

Navigational Equipment

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.

Other Systems That Will Require Power

• Microwave
• Laptop
• Refrigerator
• Chargers For Small Devices
• Lights

⚡ How Much Power Is Needed To Maintain Appliances On A Boat?

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 Power For Maintaining Electric Propulsion On A Boat

Many types of boats can be fitted with an electric motor, such as sailboats, job boats, powerboats, fishing boats, yachts, trawlers, etc.

Electric Outboard Engines

• If your boat’s current engine has a power output of up to 135 horsepower (HP), you could find an electric alternative.
• So anywhere up to 97 kW engine (Kilowatts)
• In 2021, a 180 HP electric motor was released (E-Motion 180 E by Vision Marine Technologies)
• This is 134 kW 

Electric Inboard Engines

• More powerful than outboard engines
• Up to 330 HP (246 kW)
• Have to option of having a hybrid motor/engine
• Can have a hydro regeneration capability (can charge while the vessel is under sail)
• This would only be useful for non-powerboat vessels
• The range of an electric motor depends on the boat, total weight, propellor, and battery capacity
• If you go slowly, you’ll have a greater range

So how many solar panels would you need for your sailboat? First, you must consider how much sunlight you would receive daily in the region you will be sailing in.

If you need to get an idea of the amount of sunlight your area of interest will receive, check out :

http://www.bigfrogmountain.com/SunHoursPerDay.html

For instance, if the area receives only 8 hours of sunlight per day, your solar panel output would be:

2 500 Wh / 8h = 312.5 W

Therefore, your total solar panel power output needs to be 315 W.

Sailboats Vs. Electric Propulsion Boats

Electric propulsion boats, specifically the 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:

• Require a hands-on approach
• more training and practice required
• Save money on fuel and maintenance (more maintenance but lower cost in the long run)
• Have many moving parts
• More reliant on favorable weather conditions 
• At the mercy of the winds
• Tides need to be taken into account (particularly in shallow waters), and the setting up of sails.

Electric Propulsion Boats:

• Less maintenance
• Easier to operate
• Require less experience
• More costly to maintain
• Fewer components
• More space on board which can be used for other purposes
• Quieter, less noise, fumes, and vibrations

🛥️ 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:

• An electric motor – or a trolling motor, runs entirely on solar power, responsible for the propulsion
• Batteries – accountable for the power output
• Solar panels – will convert the energy emitted by the sun into usable electricity
• Solar charge controller – acts as a charger for your battery and a control board for your solar power
• Mounting hardware – what your panels will be secured to
• Converter – converts direct current (DC) into alternating current (AC)
• Solar cabling – special cables with a wider jacketing specifically for marine solar cables

Step By Step Guide: Setting Up Solar Power On A 25 ft. Pontoon

1️⃣ Select panel size, mounting bracket, and location of where you want it mounted

2️⃣ Install mounting brackets with relevant openings for solar cabling

3️⃣ Secure solar panels to mounting brackets

4️⃣ Run solar cabling

5️⃣ Connect solar cabling to the charge controller

6️⃣ Linkup the charge controller to the battery bank

7️⃣ Connect the battery bank to the converter

8️⃣ Connect the converter to trolling motor, lights, and GPS system.

9️⃣ 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

❓ FAQs

How Many Watts Of Solar Do I Need For A Boat?

This depends on the type of boat, engine, and other electrical systems you need to be powered on board the boat.

To get an idea of this, add the wattages of electrical components (motor, lights, GPS, etc.) and multiply each by the time they are used in the day. To get exact numbers, use our marine solar calculator.

What Size of Solar Panel Is Required To Charge My Boat Battery?

The answer to this question would be contingent on the following:

• How many watt-hours do you need per day (to power your electrical components)
• How much sunlight do you receive per day
• How much space on your boat do you have for solar panels
• How many batteries will need charging

Are There Ways I Can Save Power On My Boat?

• Use power-efficient appliances (laptops, fridges, LED lights, etc.)
• Only use things when necessary (don’t leave anything running while not in use)
• Only install the necessary items
• Use your sails more frequently
• Try not to use AC power
• Avoid using the microwave

What Are The Three Types Of Solar Panels?

• Monocrystalline
• Polycrystalline
• Amaphorus

These panels are classified by the cell type (mentioned above) used in them.

Can Solar Panels Operate On Cloudy Days?

Panels will still be able to harvest solar energy on cloudy days, although it will be lower compared to a clear sunny day.

Can Solar Panel Sizes Be Customized?

Solar panels can be cut into custom sizes within reason. Still, the custom panels will be more expensive than the standard-sized ones.

How Do I Clean My Solar Panels?

Rain should suffice as a cleaning agent, but more stubborn dirt or droppings can be cleaned using room-temperature water, mild soap, and a soft sponge.

Does Salt and Sea Air Affect Solar Panels?

Ordinary solar panels, like the ones you would find on land, do not respond well to the seaside conditions. The moisture and salt air cause corrosion, malfunction, and a complete technical breakdown of the panel.

Are Marine Solar Panels Made From Different Or Specialized Materials?

As mentioned, ordinary solar panels are prone to corrosion in a coastal marine environment. Marine solar panels are therefore made from special non-corrosive components. All the components, from nuts and bolts to the panels themselves, need to be non-corrosive.

Will Solar Panels Affect The Aerodynamics Of My Boat?

Rigid solar panels are said to create more of a hindrance when it comes to the aerodynamics of a boat.

This is why many sailors opt for flexible solar paneling. Suppose your boat is powered entirely by solar power. In that case, speed won’t be a high priority, so aerodynamics shouldn’t be a cause for concern.

The placement and size of solar paneling will also play a role in the effect on aerodynamics. But again, these things will be relative to the boat in question.

🗣 Final Words

So to recap, we looked at some key points in determining how much solar is needed for a boat:

1️⃣ The systems most pleasure mariners will need to power are the engine, batteries, and navigational equipment.

2️⃣ We looked at power requirements for onboard appliances and electric propulsion.

3️⃣ Our hypothetical 25 ft pontoon example gave us a solar requirement of 1100 Wh.

It may seem daunting to install solar panels, but it is on the rise. Use our marine solar calculator to determine your boat’s power requirements.

Know that you know how much power you need. Next is how to hook up the solar panels you require in your array to make renewable energy a reality on the water.