How Much Solar Power Do You Need On A Boat? 10 Tips!

When sailing off-shore for days at a time, you will need some type of power. There are a few different options for that but the most common option is solar. Solar is a great way to power your sailboat.

As a general rule, every 10 feet of the boat needs 100 watts of power. For example, a 30-foot boat will need 300 watts of power. This is dependent on how much power your boat is using. You will have to calculate how much power your boat is drawing to be sure you have enough solar power.

Each sailboat is going to have a different amount of power being used. The typical off-shore sailboat will be about 100 watts per 10 feet. Keep reading to find out exactly how much power your need. Let’s start with some basic knowledge.

Amps vs Watts vs Volts

Amps refer to the current running through a wire. Watt is the rate of energy an item will use. Volts are the pressure used to force electrons through the wire. The formula Amps (A) times Volts (V) is for calculating Watts (W) or A*V=W.

These three terms will be essential in calculating your boat’s power needs. Let’s look at a basic example.

Your boat has a 1200-watt microwave and it is connected to your 120-volt AC circuit. Input these numbers into the formula A*V=W to find the amperage. A*120= 1200. Now, take 1200 divided by 120 to get A. A= 10 or 10 amps. This microwave will draw 10 amps of power when running.

Knowing these terms is going to help you calculate all of your boat’s power needs.

Click Here To See My Article On The Best Solar Panels For Your Boat!

How Much Power Are You Using?

To calculate how much power you are using, look at all the appliances that draw power on your boat. The label should tell you what the power consumption is. If it does not, you can purchase a power meter and monitor what each item uses.

For example, look at the table below. It shows some typical items that may be on a sailboat and calculates their usage.

Fridge100 watts 800 watts
Light60 watts480 watts
Fan75 watts600 watts
Navigation Panel2 watts16 watts
Microwave1200 watts9600 watts
TOTAL1437 watts11496 watts

This total watts calculation of 11496, is calculated as if these 5 items were on for 8 hours straight. This is clearly not the case. Also, a 60-watt lightbulb is not normally used in a sailboat anymore, they use LEDs now. To make it more clear take a 1200-watt microwave and divide it by 60, which gives you 20 watts per minute. Most microwaves are on for no more than 2 minutes. That means when using your microwave you are using less power than a light that is on for an hour.

If you prefer, you can break down your power consumption into minutes and calculate what you think you actually use, instead of a basic 8-hour estimate.

These are some of the things to consider when trying to decide how much power you need for a sailboat. Now that we know the power consumption let’s look at what solar panels you need.

What Size Solar System Do I Need For A Boat?

The size of the solar setup you need on your boat will depend on how much power your boat consumes. If you have a 25-foot boat consuming 300 watts of power, you will need a 300-watt system. This can consist of 1 300-watt panel or 3 100-watt panels.

When setting up a solar system on your boat you will need a few basic components.

  • Solar Panel – This will capture the sun’s rays and make energy
  • Charge Controller – The charge controller will show you the amps your boat is bringing in and also protect your batteries from being overcharged
  • Battery Bank – The battery bank is where all of the power gets stored. If you have a small boat, you may only have one battery
  • Inverter – Inverters will take your battery power and turn it into the correct voltage for the items attached

A basic diagram of how the power will flow from the sun to the parts of the boat is shown below.

As you can see from the image above, boat wiring is not super complicated. The difficulty comes from calculating what you need and actually installing all of the components.

Can A Sailboat Run On Solar Power Alone?

If the power consumption of the boat is less than the amperage coming in from the solar panels, the boat can run on solar power alone. When the consumption of power is more than what is coming in, your batteries will begin to lose their charge. Reduce power usage to allow your batteries to recharge.

Solar panels take the sun’s rays and convert that into usable energy. You can then harness this energy to power your boat. There are a few things to consider when going full solar.

Will you be in a sunny climate? If you are going to be north in the cold waters, there will probably not be that much sun. If your boat is strictly solar power, you will need to consider this.

Now, most boats have solar power but can also plug into a dock somewhere and charge their batteries that way. This will keep you from relying on the sun on 100 percent of the time. When planning a long trip at sea remember to make sure your batteries are fully charged before leaving.

10 Power-Saving Tips For Your Sailboat

1. Convert old lights to LED

2. Only use energy-efficient laptops

3. Do not leave anything running while not being used

4. Find a marine fridge/freezer that uses minimal energy

5. Only install items that are necessary and not a luxury

6. Sail more

7. Unplug electronics when not using

8. Grill food don’t microwave

9. No AC onboard

10. Use solar-powered vents

All of the items listed above will help cut down on power usage. This will help keep your batteries charged for when you really need them.

Where Do You Mount Solar Panels On A Boat?

There are multiple spots you can mount a solar panel on a boat. The main thing to remember is to mount your solar panels in a spot that gets the most sun and won’t be blocked by anything. Being able to lift and point your panels at the sun is a good idea as well.

A lot of people that operate sailboats will mount their solar panels over the cockpit of the boat. They will also, set it up where they can raise one end of the panels and point it at the sun while it moves throughout the day.

This is a great way to maximize your solar power.

Final Thoughts

When it comes to powering your sailboat electronics, solar is a must. Unless you know you will be plugging into shore power every night. I still recommend solar power to help cut down on the world’s energy usage, but that’s up to you.


Boatlifehq owner and author/editor of this article.

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