How Do Boats Have Electricity? Explained For Beginners

If you consider that a boat is an independent entity and not generally connected to the land, the problem of how to supply your boat with electricity is a concern.

You will first need to calculate your daily average consumption by listing the devices that you will use and the amps or units they consume.

By calculating your average consumption, you will be able to determine the amount of electricity your boat needs to produce to run the equipment you need.

Why Your Boat Needs Electricity:

You will need electricity on your boat to power even the most basic of safety equipment, like navigation lights, and to start your engine. For longer trips, electricity can be used to power a fridge, for internal lighting and to power marine navigation equipment, and even to charge your phone.

In this article, we will discuss the ways that boats get their electricity:

3 Main Ways Boats Get Electricity:

Firstly, for you to have electricity on your boat, you will need a battery or a battery bank to store any electricity generated by the source of power.

Just like your car, your boat has an engine, and you will need stored electricity just to start the motor!

Electricity for navigation, refrigeration, lights, or other electrical items requires a power source.

The following are the three main sources of power on a boat:

  1. Shore-Power: provides electricity directly to your boat via a heavy-duty cable which you plug into a socket from your boat to a connection on the shore or dock.
  2. Engine-Generated Power: provides electricity to your boat by running your engine through an alternator, or if you have one installed, by running your generator.
  3. Renewable Energy: can be in the form of solar power, wind power, or even hydro or water power.

Whichever way your boat generates electricity, your boat’s batteries are the mainstay of a good electrical system. Powerboats used as a weekend runabout or for short fishing trips may only need one battery, although two are better from a safety point of view.

However, vessels going offshore (such as sailing yachts) or even anchoring for the weekend in a secluded bay will need a dedicated engine start battery and at least one other ‘house’ battery, if not more.

What Happens If a Boat Runs Out Of Power?

The main problem you will have if your boat runs out of power is that your engine will not start!

In addition, if your boat runs out of power, nothing electrical will work. This includes safety equipment like navigation lights, interior lighting, and electronic navigation aids.

This is why, when crossing oceans or when you plan to sail out of sight of land, it is a good idea from a safety point of view to plot your course on a paper chart with a battery-powered (or handheld) GPS to use as a backup.

What Kind Of Electrical Devices Can Be Used On Boats?

Generally, boats run on a 12-volt or DC (direct current) system. Compare this to your home, which depending on where you are in the world, is either a 110 or 220-volt system, also known as AC (alternating current).

Simply put, you cannot run your normal electrical home appliances on your boat unless you are plugged into shore power, or you have installed an inverter.

If you have installed a marine-approved inverter, then your 12-volt system can be used to create AC power. This means you can use your normal household appliances. However, using normal household appliances will also increase your use of electricity, which means your batteries will need charging more often.

Nowadays, there are many appliances and electrical devices that are designed to work on a 12-volt system. Apart from specific boating electronics, these appliances can include 12v fridges, car radios, lighting, and even electric toilets!

Top tip: LED lights use much less energy than incandescent light bulbs. Plus, in a marine environment, LED lights to stand up to vibrations much better than the alternatives.

They also stay cool to the touch, last far longer than normal bulbs, and are less prone to water damage.

Do All Boats Have Electricity?

Most boats, especially those with engines, will have electricity.

However, small boats with no engine or those powered by a small outboard engine will not have the capability to produce electricity unless they have been equipped with alternative sources of producing electricity like solar panels or a wind generator.

How Do Boats Recharge Their Batteries On The Water?

There are several ways to keep your batteries charged while you are out on the water.

Each of them has its advantages and disadvantages:

Your Engine:

Your boat’s engine produces electricity when used with an alternator.

The alternator converts mechanical energy into electrical energy and is a critical component for keeping your batteries charged.

  • Pros: When you are running your engine, your batteries will charge automatically.
  • Cons: Running your engine when not necessary use fuel and makes a lot of noise.

In addition, running your engine at low revs may cause damage to your engine.

A Generator:

A generator can be fixed or portable and can be run at any time to give your batteries a boost.

  • Pros: A generator can be run at any time.
  • Cons: Generators can be noisy, and they use fossil fuel, either diesel or gasoline, which can become expensive.

Solar Panels:

Electricity is converted from solar energy, which passes through solar panels.

This is done through photovoltaic cells, which are attached to the panels themselves. Because Solar panels are getting more accessible and easier to use, they are a great addition to your boat.

  • Pros: Once installed, they provide free energy to keep your batteries charged.
  • Cons: They need the sun to produce energy, so they are not a reliable source of electricity production when used on their own.

Wind Generator:

Wind generators use the wind to produce reusable energy when used with an alternator.

  • Pros: If there is a strong wind, or you are underway, they can produce more electricity than solar panels.
  • Cons: If there is no wind, there is no electricity.

In addition, some models are noisy, they need regular maintenance, and the moving blades can be a hazard on a boat.


Water-powered generators or hydro-generators produce energy by converting water flow into electricity via an alternator.

  • Pros: They produce free electricity while on the move.
  • Cons: They do not produce electricity when at anchor and may cause ‘drag’ or the boat to move more slowly when sailing.

For small boats, charging your battery from your engine will more than likely suffice. However, for larger boats, or if you are planning weekends away, then a combination of the above is recommended.

It’s a good idea to consult with an expert about your boating electricity needs.

Final Thoughts:

In addition to keeping your batteries charged, there are a few other steps you can take to keep your batteries happy and healthy:

  • If you are using more than one battery in a bank, don’t mix battery types or mix old and new batteries.
  • Make sure you keep your batteries clean and dry.
  • If you are wintering your boat, make sure you disconnect your batteries and store them in a cool, dry place during the off-season.
  • Check for corrosion. It can be cleaned off using a wire brush in combination with a solution of baking soda and water.


Renewable Energy – Sailors of the Sea

12 Volt Electrical Systems – Boast US

Power Generation – World Cruising Wiki

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