Solar Boat: What Size Solar System Does Your Boat Need?

Capt. Jim Greer finished a 7,200-mile cruise, and he did it running his 48-foot trihull purely on solar power. 

His longest run was 142 miles in 42 hours nonstop, day and night, crossing the Gulf of Mexico.

If that's not impressive then we don't know what is.

Video: Jim Greer's Solar Boat Recollection Story

You may be wondering how exactly he did it? 

Well, in this article we aim to teach you what size solar system you need for your solar boat.

Ultimately, if you want to go on a long voyage like Capt. Jim Greer, you are going to need some serious battery capacity. 

This article is instead aimed towards hobbyists looking to equip their watercraft with some basic onboard solar to power certain smaller appliances on their solar boat.

How to Calculate the Amount of Solar Your Boat Needs?


Knowing how much solar power you need on your boat all comes down to the number of appliances you want reliant on solar in the first place. 

Now, Capt. Jim Greer has got some serious solar equipment to make his boat completely reliant on solar energy.

However, most boat owners would feel satisfied knowing that their most important appliances are reliant on the sun, which there's an abundance of. 

So how exactly do we know how much solar power for boats we need? 

First, you've got to figure out how much power your boat's appliances are using.

Generally, boats that host various watersports activities onboard require much more appliances to keep everything operating smoothly.

We will assume for this example that you own a common sailing boat, that you will take out for the month. 

 Appliance Power consumption Hours used Total Watt Hours
Mini fridge 60W
24 1440
Lightbulb 60W
6 360
Fan 90W
4 360
34 2160


Go ahead and use the same layout as us to create your own list. 

To get the total watt hours of each appliance, simply times total wattage of your appliance by the amount of time that you use it for. 

For example, a 60W mini-fridge used for 24 hours = 1440Wh. 

Once you have gone through all your boats appliances and the amount of time you aim to use them for, you should be left with a total Wh (watt hour).  

Now keep in mind our example is very limited (for simplicity's sake), so if you want to make sure you have the right sized solar system, be sure to add ALL the appliances you want to be powered by solar.

Now that we understand how much electricity our boat consumes we can figure out how many solar panels for boats.
It all comes down to using this formula:

Let's start with our monthly electric usage.

We have already established that our boat uses about 2160Wh a day. Let's times this by 30 days (a month).

2160 x 30 = 64,800Wh or 64.8kWh. 

Next we need to establish how many peak sun hours our area gets. 

Where are your sailing? 

Put that location in Global Solar Atlas to figure out how many peak sun hours your location experiences. 

For our example we will be sailing off the coast of California. 

Using Global Solar Atlas we can see that our area receives around 5.2 peak sun hours a day. 

Lets multiply that number by 30 to get the monthly reading.

5.2 X 30 = 156 peak monthly sun hours.

Remember, if you plan to move around a lot you will need to average out the total amount of peak sun hours your boat will be experiencing based on its location.

Now we can simply use our formula to figure out the amount of solar panels for boats offset electricity usage.

(64.8/156) X 1000 = 415 watts

This means you will need a total of 415 watts to power your boats onboard equipment. 

You can complete the formula by dividing you're result by the power rating of your proposed solar panels, this will give you the amount of solar panels for boats required. 

Let's say we want to mount 100 watt panels onboard. 

415/100 = 4.15 panels required (lets round that off to 4). 

How to Calculate the Amount of Battery Power Your Solar Boat Needs?


Remember, not everyday will be sunny and night time will come. What do you do then? How will you power your boats appliances?

This is where marine boat batteries come into play. 

Again you will require the table we already created above to figure this out. Take note of your daily watt hours usage.

First, select your battery bank voltage size:

  • 12V – Smaller systems
  • 24V – 48V – Medium to large systems

We will use 12 volts for our boat. 

2160Wh divided by 12 volts = 180Ah (amp hours)

Now let's account for days of autonomy. We do this to assure we have enough power on overcast days, where the sun is not able to power our devices or charge our battery. 

180 X 2 days = 360Ah. 

360Ah would be more than sufficient in power our boats devices at night, and in a worst case scenario, during an extended period of 2 days without sun. 

(Please note: we did not account for inefficiencies and temperature coefficients in our calculations.)


Can I Use a BLUETTI Solar Generator on a Solar Boat?

A Bluetti Solar generator could absolutely be used on your boat. The overall investment would be cheaper and installation costs would be non existent. 

You could simply plug your required appliances into your solar generator and power them directly. 



You could then use our PV 200 Watt solar panels to recharge your generator whenever it is sunny. 

Final Thoughts

We would recommend using a Bluetti solar generator on shorter sailing trips.

However, if you plan to go out on extended expeditions we would definitely recommend getting a full on fixed solar system installed, with a large battery capacity. 

If you would like to read more about solar power for boats check out this article


1. How does a solar boat work?
Boats have traditionally been propelled by manpower, such as using paddles, by wind or motor, such as using gasoline. ... Therefore, this means that solar boats are boats that get their energy from the sun – by the use of solar panels and storage batteries to transform sunlight into electrical power, which powers the boat.

2. Are solar panels on a boat worth it?
There are numerous benefits to powering your boat with solar energy. One of the most attractive benefits of marine solar power systems is the monetary savings. You'll need to invest money upfront to purchase solar equipment; however, once it's up and running, you'll be generating free electricity for your boat.

3. What is a solar yacht?
Solar boats use renewable energy from the sun to run their motors, electrical systems, and onboard appliances. They do not use petrol/diesel generators or engines and meet all their power needs using solar panels and batteries.