Mar 22, 2021

A guide to powering your sailing boat in 2021

Published by: Kyle Martin
Cover photo
Energy for navigation, refrigeration, lights or other electrical items requires a reliable power source on any sailing boat or yacht. Depending on the desired luxury and convenience on the boat, energy consumption may vary greatly. If you have an engine, it’s possible to charge the batteries. But a boat’s engine will use almost as much fuel to charge batteries as it does when motoring. Idling your engine still produces emissions and pollutants that negatively affect our environment and our health. Running your engine purely for charging batteries can also harm your engine, as it is not designed to run below its rated level.
Before choosing which energy system is best for your needs, you first need to establish:
  • What are you trying to accomplish (power navigation, run refrigeration, etc.)?
  • How much electricity do you require?
  • Do you need to modify your boat’s electrical system to meet those requirements?
  • Do you have the appropriate weather conditions (wind, sun, etc.) to “fuel” the generator?
Let’s review the different sources for energy generation and storage on boats and yachts!


Batteries are required to store the electrical energy received from the generator or other sources in order to dispatch it depending on electrical devices demand. The batteries provide a real-time and on-demand reply to your boat electrical requirements.
Marine batteries are designed specifically for use on a boat, with heavier plates and robust construction designed to withstand the vibration and pounding that can occur onboard. For this reason, marine batteries are usually more expensive than automobile batteries, which can tempt some boat owners to purchase an auto battery instead of a marine battery. Don’t make that poor decision. A marine battery will last longer and be more reliable than an auto battery in a boat.
There are several types of batteries available. The main ones are:
  1. Open lead-acid batteries, the most common and oldest technology for cruising sailboat. The electrolyte fluid level has to be checked on a regular basis.
  2. Sealed lead (or lead-calcium; valve-regulated lead-acid VRLA) batteries require less maintenance due to the fact that no liquid level check is needed. The chemical reaction ensures battery operation for the lifetime indicated by the manufacturer.
  3. AGM and gel batteries. The liquid electrolyte is replaced by a gelled solution, there is no risk of leakage or liquid level issue, the performances are higher and the lifetime is better. But this type of batteries are heavier and more expensive.
  4. Lithium-ion batteries. Lithium batteries have a high specific energy density, which allows them to store more energy in batteries of smaller size and mass. They are also distinguished by high current output and have a number of advantages. But even their charge lasts for a very limited time. The major constraint to their development is a high selling price.
You should choose your marine battery based on the purpose of the battery:
  1. Marine starting batteries provide quick but powerful spurts of energy over short periods of time and are designed to start the engine and be rapidly recharged by the engine alternator. A starting battery should not be used for trolling motors or powering appliances.
  2. Marine deep cycle batteries are designed to discharge slowly over a long period of time and to withstand several hundred charging and discharging cycles. A deep cycle battery is the right choice for powering an electric trolling motor and other battery-powered accessories such as audio systems, a windlass, depth finders, fish locators, and appliances. Deep cycle batteries should not be substituted for starting batteries.
  3. Marine dual-purpose batteries combine the performance of starting and deep cycle battery and are a good choice on smaller when there’s no room for two batteries. While they're able to perform the tasks of a starting battery and deep cycle battery, they're not as efficient as separate batteries.


During sailing, the batteries need to be charged. It is a good idea to have at least two independent energy sources. In general, all methods of autonomous charging can be divided into two groups:
  • Renewable energy sources (solar panels, wind, hydro generators, hydrogen fuel cell generators)
  • Fossil-fuel powered sources (diesel generators, petrol generators, etc)

A renewable source of generation is a good option and a good safety backup for boats. There are several types of systems you can use including wind generators, solar panels, water generators, or a combination. Some systems can keep your battery fully charged while your boat sits on the trailer, on a mooring or at the dock, or can be used during long journeys while you are underway.
Let’s go through the renewable sources one-by-one.
Solar panels can be used on small and large boats effectively, they weigh relatively little, and can be flexible. But there are also many risks, especially for a small yacht. Primarily the risk of damage to the panel itself, controller, cable or contacts. The second is the lack of sun. It may happen that for several days the sun does not shine, or you go in such courses that you cannot effectively direct the panels to the sun – they stay in the shade of the sails. On a positive note, they require minimal maintenance, don’t make noise, last up to 25 years or more, and are safe. In general, solar panels are a good complement with some other solution to produce electricity.
Solar sails (solar cloth sails) are being made around the world, where photovoltaic film is attached to each side of the sail.
Water-powered generators are relatively inexpensive but require a flow rate to give charge. There are two main types: towed spinner generators and shaft generators. With both, however, a minimum speed of 4 knots is recommended, as below this speed, the energy generated is negligible. At low speed of the boat, there is no charge, but there is resistance. There is also a risk of damage - collision with floating objects and breakdown of the propeller. Plus, the risk of damaging of cables, charger and contacts.
Wind generators use the apparent wind to produce renewable electricity through an alternator. They can be fixed on a mast or gantry. Wind generators have the potential to produce power 24 hours a day whether sailing or at anchor. If there is a strong wind, or you are underway, they can usually put out more current than solar panels. Wind generators, however, can be noisy, require regular maintenance and have the potential danger of rotating blades. Because of the huge sails of a sailing boat and long booms it is easy to mechanically damage such a generator.
Methanol fuel cells have good advantages – they work quietly and rather economically. They can be located inside the yacht and continue to work with any wind conditions and sea state. They don’t require too much special care while operating, but they do fail sometimes. Although we listed methanol fuel cells as renewable energy source, they do emit some carbon dioxide.
One of the most promising technologies for boats and yachts – hydrogen fuel cell generators. They are a relatively new, progressive energy source that run on renewable fuel. In principle, in the future, hydrogen could be generated even on board the yacht itself, increasing the autonomy. Of course, there are some big limitations that must be overcome, as the electrolysis process is relatively inefficient. Among the advantages – hydrogen fuel cells are lightweight and compact systems that provide a high charge current (the UP400 model gives 32 A). It works in extreme conditions, is quiet and provides clean energy without emissions.
There are non-renewable sources available and quite often they tend to be more friendly for your wallet. Of the advantages, fossil-fuel generators can charge rather quickly. But more often than not, this is where the pros are over. This energy source is the least environmentally friendly of all. It runs on fossil fuels, has a very unpleasant exhaust, from which the head constantly hurts. It does not work while boat is heeling or bumping. Read more about the advantages and disadvantages of diesel generators here.

Whether you are long-range cruising folk or enjoy the weekend getaway on a boat, energy is a sensitive topic for all boats. You get what you pay for, so consider your options carefully and it’s always best to consult an expert.

Photo source.

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