Comparing 6 Energy Sources For Electricity On A Sailboat

We usually have all sorts of equipment onboard our sailboats that require electricity, like navigation instruments, navigation lights, VHF Radios, refrigeration, interior lighting, and much more. We also want to be able to charge our devices, laptops, cameras, drones, and other appliances onboard.

And for that we need electricity.

Sailboats generally get their electricity from shore power in a marina or from their batteries at sea. The batteries get power from the main engine’s standard alternator, often combined with one or more of the following sources:

• Additional alternator
• Generator
• Solar panels
• Wind generator
• Hydrogenerator
• Fuel cell

We tend to choose our sailboat’s energy source based on how much power the equipment onboard requires. It is also important to consider what else we want to power up onboard, especially if we’re going to plug in 110V or 230V equipment. Let us take a closer look at how we get electricity onboard.

Electricity onboard a sailboat and why we need it

We need electricity on our sailboats for many reasons. The engine requires power to start, and our navigation equipment and sailing instruments need electricity to operate. We must keep our navigation lights on when it gets dark, and sometimes we want to have the interior lights on.

Another super essential and power-hungry device we ideally want to keep running is the fridge. We don’t want our food to go bad, and we certainly want to avoid having to drink warm beer. Since we live in modern times, we also want to charge all our devices and toys as well.

In the end, our sailboat has become quite power-hungry for electricity, and when we leave the shore and unplug the shore power, we have to rely on our batteries to supply the energy we need. Let us have a look at some common equipment often found onboard sailboats.

Equipment that requires electricity onboard a sailboat

If you are slightly unfamiliar with sailboats, you may wonder: What equipment do we often have that requires electricity? Check out this list I made from the top of my head. Remember that it is highly individual how much stuff we run on our boats, but these are pretty typical items:

• Engine starter
• Windlass
• Navigation lights
• Chart plotter
• Sailing instruments
• Autopilot
• VHF Radio
• AIS
• Sound system
• Interior lightning
• Water pumps
• Bilge pumps
• Refrigerator
• Laptop charger
• Phone and tablet chargers
• Camera chargers
• Drone chargers
• Head torch chargers
• 110V/220V inverter

This list can get endless. We definitely want a reliable way to keep us supplied with energy, and we also need a way to store this energy.

Sailboat batteries and how to charge them

The batteries on a sailboat get charged by the engine’s alternator by standard. Relying on the alternator is fine if you don’t require too much energy to power your equipment onboard and don’t mind running the engine often.

Modern sailboats usually carry several batteries. It is standard practice to have one or two batteries dedicated to starting the engine and a separate series of batteries, called house bank, to supply the rest of our needs. It is a good idea to separate the starter battery and the house bank to avoid draining the starter battery by mistake.

The starting battery is usually 12V (DC voltage) for most sailboats with a diesel or petrol engine. Our house bank can sometimes be either 12V or 24V, depending on your sailboat setup.

But if you are a liveaboard sailor or have lots of power-hungry stuff and equipment, it quickly gets tedious to run the engine all the time to keep the batteries charged up. Luckily, there are many excellent additional alternatives to keep your batteries charged without running the main engine.

This brings us to the next topic. Let’s look at some excellent options to keep our sailboat fed with energy.

6 energy sources for sailboats compared

It is pretty common to have a combination of two or more of the following energy sources. They all have pros and cons, but it is hard to tell which one is the best as it depends on yourself and your needs.

I am personally a huge fan of solar panels, and I get 95% of all my energy from this wonderful and sustainable source. And my list of equipment that requires electricity is way longer than the one earlier in this article…

Let us have a look at each of the six most common additional sources of power used on sailboats:

Main Engine Alternators

Most sailboats have a main engine, and the main engine has an alternator that generates electricity when running. The alternator is connected to the batteries and will keep charging them for as long as you run the machine in most cases.

Standard alternators don’t always give a high enough output to charge larger battery banks within the timeframe we have the engine running. One good option here is to add a secondary high-output alternator, which can be great in combination with another power source.

Generator

Generators or gen-sets are typically found on larger sailboats with plenty of space to install them. It works similarly to the main engine but generally has a much higher output of 110V or 220V.

The generator then supplies your mains power the same way as if you plugged your cable into shore power at the key or marina. Generators come in various sizes with different outputs. Some are units you can move around, while others require to be permanently installed.

Solar Panels

Solar panels are great and can give you significant amounts of energy, especially when sailing in tropical and sunny climates. They require some space and careful placement to be efficient, as shading significantly reduces their output. And on a sailboat, many things can give shade, especially the mast and our rigging.

A common practice is placing solar panels on top of the sprayhood, bimini, or on a separate solar arch on the back of the boat. You can, of course, do a combination and even use flexible panels on the front deck.

I have also seen many people mounting panels on the sides of the boat with a mechanism to flip them up to face the sun when needed. You need additional solar chargers to feed electricity from the solar panels to the batteries, and the best option here is to use MPPT chargers.

Wind Generator

Wind generators can be great if you sail in a windy area like the Caribbean. They can constantly run 24/7 as long as there are sufficient winds, which can be very helpful. Especially at night when solar panels won’t give you any output, and you don’t want to run the engine or generator to wake up everyone on the boat.

However, they won’t give you high power output and may not cover your needs unless you use electricity sparely. They can be great if you have the space to mount one or two in addition to another source. Just make sure not to mount them in a way that can shade the solar panels.

DuoGen makes a hybrid that can work as wind and hydro generator, which can be a good option for many, but they start at a relatively high price.

Hydrogenerator

A hydro generator generates power through its propeller when dragged through the water. Hydro generators often look like a small outboard engine mounted on the back of a sailboat, but you can also get them in variations that can be permanently installed underwater.

The hydro generator will generate electricity as long as the boat moves through the water, but not when you are at anchor. You can typically expect an output of around 10A when sailing, which can be very helpful underway.

If you spend a lot of time at anchor, as most cruisers do, your best bet is probably to combine the hydro generator with another source like solar or wind generation.

Fuel Cell

A less popular source of electricity is the methanol fuel cell. It uses a chemical process to generate energy that requires methanol as fuel. They usually come as standalone units and are simple to install, but the output is relatively low compared to some of our other alternatives.

Another thing to consider is the need to carry methanol fuel onboard, which is highly flammable. Some people like them a lot because they don’t make any noise, can be placed anywhere, and require little maintenance. There are also fuel cells that run on propane instead of methanol.

Final Words

Everyone has different needs onboard their sailboats regarding how much energy they require to run their electric equipment. Especially cruisers and liveaboards have relatively high energy demands to keep the electronics alive, and relying on the standard alternator isn’t feasible.

From my experience, solar panels are the way to go if you intend to sail in sunny climates, and many cruisers seem to agree. The sun is an infinite source of green energy, and given that you can fit enough panels, they will be able to supply all the renewable power you want.

I have two 285W solar panels hooked up to a 50A MPPT charger, and I easily get 25-50A of power on a good sunny day, enough to leave my lithium batteries topped up by mid-day.

Solar panels often overperform way above their stated output, as seen in the solar charger dashboard in the picture below.

Combine solar with another source, and you have great redundancy for cloudy days. I am very skeptical about fuel cells, however. Still, technology is moving forward rapidly, and I think we will start to see hydrogen fuel cells becoming feasible in the future, which is exciting!

I am curious to know, how do you supply your sailboat with electricity? Leave a comment below!

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