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The issue of the safeguard of our resources is more and more topical and, on a boat, its impact is even greater. A sustainable and respectful approach to the environment affects also the sound management of on board resources (like at home) i.e. power and water.

While boarding a boat, in fact, we need to be aware that there are some bad habits of ours that must necessarily be modified. That is when we do not to switch the light off when we leave a room. Or when we waste litres and litres of water when we do the washing up or when we brush our teeth or have a shower instead of opening and closing the tap based on the water we really need!

So, on a boat this “habits” make a great deal of difference and, if we don’t care about them, they can negatively affect, even heavily, our daily well-being. Let’s see how.


On board electrical systems are powered by 12V direct current (or 24V according to the system), the same as your car cigarette lighter socket. This is because electrical appliances are powered by batteries, exactly as your car.

Batteries supply all the energy required by any appliances or utilities. However, as batteries are accumulators whose charge does not last forever, if they run out of energy due to an inefficient use of on board equipment, we wouldn’t have cold drinks or food properly stored in fridge, nor running water because the pump wouldn’t work, nor fully charged mobiles. Not to mention even more important equipment such as radio, GPS as well as all navigational instruments.

Also the engine needs a battery to start, usually a dedicated one. This is why a battery switchis provided to “connect” them (in parallel) in case of engine battery failure. They are usually located under the dinette access ladder or in an stern cabin or under the chart table.

Therefore make sure the engine battery is separated from the utilities battery.

When the engine is on and above a given RPM (approximately1200/1500), the alternator charges all the batteries through a charge distributor (the same as your car). Ideally batteries should be charged while sailing but sometimes you can hear the noise of the engine running even when the boat is stationary.

On board power availability is not the same as at home. Normally 220V power supply is only available when the boat docks at the port bollards.

I say “normally” as boats can be equipped with a current generator and a 220V system which provide alternating current also when the boat is far from the dock.

It goes without saying that if we want to use a 1400W hair dryer- not to mention the fact that we could count on a much better and natural element such as a warm summer breeze – we must be aware we can use it only when docked in a port.

Thanks to an inverter – fixed or portable – direct current is converted into alternating current thus making 220V available even when the boat is not docked at the port bollards. Pay attention, however, as the inverter increases consumption significantly.

Different types of inverters are available. Up to 4/500W the inverter is powered via the cigarette lighter socket. Beyond that, it is better to power it directly via batteries to avoid cables overheating, which is very dangerous as a probable cause of fire on board (pay attention to burning smell).

Each battery comes with a certain capacity in Ampere hour, which is its charge. Sum up the Ampere required by any utilities (such as lamps, fridge, fresh water pump, winch, VHF, etc.) to make sure they don’t exceed the charge you can draw from the battery. Power is usually expressed in W.

The formula for calculating consumption is: Ampere = watt / volt (on board system voltage is usually 12 or 24).

Battery lifetime is “measurable” in charge cycles (not in years). However they generally reach the end of their useful life after 4/5 years.

Some boats are provided with solar panels or wind plants that contribute to charge batteries. But, regardless of energy-supply boat equipment, there are two main things we always have to pay close attention to:

First: lights in thecabins, toilets or dinette (i.e. the living room).

Many are halogen instead of led or incandescent, which increases consumption. I recommend to replace them all with led lights.

Note: halogen lights are beautiful. However, each of them is 20V on average (twice the power of incandescent ones). If we switch on all the dinette lights, consumption will be about 160W, which is 13.3 Ampere/hour. If these lights were on for 4 hours, consumption would be about 53 Ah i.e. half the charge of a 100 Ah battery. What do I recommend? To switch off all the lights you don’t need.

Second: the fridge

When the compressor starts and stops repeatedly, power consumption increases. So avoid to open the fridge if it is not necessary, as inner temperature rises thus starting the compressor.

The little trick is never to keep the fridge too empty. On the contrary, the fuller the fridge is, the better the food is stored. During the night, contrary to what many people do, you don’t need to turn it off. This because, apart from the risk of spoiling the stored food, much more energy is needed the following day to reach the required temperature. Setting the fridge at a medium cooling temperature is the ideal solution.

Of course, there is nothing wrong in turning the fridge off at night. The following day, however, don’t forget to turn the fridge on only when the boat is sailing to improve battery safeguarding. Be aware that on board equipment should automatically turn it off if e.g. utility consumption makes the system voltage fall below 11.3/11.8V.

To keep battery charge under control, consider that the voltmeter should ideally supply 12 to 12.8V at operation while, under charging conditions, from 13.5 to 13.8V.


This is also important, although not so important as power.

It is not essential as the water in the tanks cannot be considered drinking water by definition, especially in case of rented boats, which may not undergo the careful maintenance and cleaning usually provided by a meticulous shipowner. I might recommend to add a glass of sodium hypochlorite (amuchina) every 300 l of water, but even this cannot make it safe to drink.

Water in these tanks is mainly used to manage everyday needs: showers, wash basin, washing-up, etc. They can store 2/300 l and more. A 14-15m-boat has on average tanks containing 600/1000 l, depending on the model.

If you consider that at home normally 80 l of water on average are used for a single shower, on a boat, after the whole crew (e.g. 8 people) has taken a shower, all water stock has gone! This would mean to return to port to load water losing time and money.

If you don’t want to go every day back and forth from ports to stock water (and not all ports can supply water as it depends on navigation areas), also this resource must be carefully managed.

For example when you brush your teeth you just need to open the tap once to wet your brush and once to rinse. Purists fill a glass of water and brush their teeth on the deck, while watching the sea.

Another important opportunity to save water is when you do the washing-up.

The little trick is: remove the leftovers and put them in the bin. Tie pans and pots using a rope, lower them into the sea and secure them firmly somewhere at the stern. After that it will be surely easier to do the washing-up saving both (water biodegradable) detergent and water. Ideally the “washing cycle” should start and end into the sea.

Many boats are provided with a foot-operated pump installed next to the wash-basin. A dedicated tap provides seawater when the pump is operated. So, if you do not want to sit at the stern – which is more practical and enjoyable – salt water is available directly at the kitchen sink without wasting on board fresh water.

Last but not least: shower.

Unless weather conditions are really terrible, the best thing to do is to wash yourself in the sea. Use low-foam sea soap (or shower/shampoo) and then dive into the sea to rinse off.

These products remove sea salt and have an emollient action both on your skin and hair. Then the deck shower is perfect for a quick last rinse.

Got it! As just few litres of water are used, you don’t have to return once again to the port to stock water and everybody can enjoy the sunset in the middle of the sea.

Finally a spray conditioner may add that extra touch to your hair, but here very personal matters are involved….

As you can see these tricks are neither difficult to do nor to understand. They teach us to give value to our resources, at sea as at home.

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Bye, see you anon.


Aldo Lavezzo
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