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Power Audit

I know that this question regularly does the rounds, but what is the best way to do a power audit?

Asked by: Fiona  | 11.00am, Sunday 25 November

WW says:

There is a useful calculator tool under the "Electrics" tab but the basic principle is to look at every electrical item on board the boat; determine the power of each item and decide the average time each item will be used in a 24hr period. From this information the amount of current drawn from the batteries, expressed as Ahrs can be determined. If an inverter is used to power 230V appliances the current draw will be higher than the appliance current; the efficiency and quiescent current of the inverter needs to be added.
It is not an easy task but should give you an understanding of where the power is being used if you are having problems.

Rupert Smedley  | 12.46PM, Sunday 25 November

If you are having problems, you can probably 'cut to the chase' if you concentrate on the fridge and the lighting system as these are the major users of power on a boat.
The fridge obviously has to be on 24 hours a day but you can reduce the amount of power consumed by opting for a 12-volt model rather than a 240-volt model run through an inverter. It will be more expensive to buy but is usually worth it in the long run.
You can reduce the consumption of the lighting system by changing from filament bulbs to LED ones. These use so little power so you can afford to increase the output slightly and enjoy a better level of lighting while still saving large amounts of electricity. Switching to LED could cost around £150 for the whole boat but it might mean that your batteries last for an extra season or two.
And while on the subject f batteries, if the boat is not used over the winter, it is worth getting a solar panel to stop the voltage dropping and shortening their life. Even a relatively small 50 or 70 Watt panel will make a difference.
Other items like pumps obviously use more power when they are running but this only for short periods so the drain on the batteries is less of a worry.

Graham Booth  | 4.33PM, Sunday 25 November

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