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Boat power, how much do you really need?

The subject of electrical power for a boat is always a contentious one. Not sure why, but yachties seem to take great pride in NOT needing power.

But if you are living aboard you DO need power for a comfortable life and there is a minimum amount you need.

If for instance you want to work on your computer, watch a little TV, have water, run your fridges and freezers and still have enough power to run your navigation/anchor lights etc. We find, on Waiata we need roughly 7-10Kwh a day to operate.

Many sailors will be horrified at that saying they only have 600AH of battery and that they are fine. Well they might be as 600W an hour from their solar array would be about that power generation for a 10 hour summers day. They have just not thought about it in the same terms.

Also, if you have cloud or in autumn/Spring you’ll not get full power from your solar for 10 hours, you’ll do considerably less than this. What does this mean, well it means most of those who scoff at our 2.2Kw of solar and 1400AH battery… .run their generator daily to keep up. Whereas we don’t unless it gets bad for a few days in a row.

So how much power do you really need, well that depends on how much diesel you wish to burn and if you are going “live” onboard all year round. If like us you do intend to do this, then I can tell you you need more than we have, we still have to run the generator in spring/autumn once a week or so for an hour and we would love not to have too.

The short answer is don’t buy into minimalism on power, get the most you can afford and or fit onto your boat in terms of both generation and also storage.

I think we could benefit from a couple of wind generators, now we are getting into the trades :-).

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2 Responses

  1. “600W an hour” isn’t meaningful in terms. It’s the acceleration of power. Units are important. You probably mean “600W during peak generation” or perhaps “600 Wh / h for six hours.”

    Otherwise I mostly agree with you.

    My experience with wind generators has been poor. Mostly they are good for shading solar panels. If you’re passagemaking with wind forward of the beam they can help. Otherwise, not so much. Consider apparent wind sailing downwind and anchoring in protected places.

    1. Now, this is my area of expertise.

      And sorry 609W for an hour does make sense, it equals 600Wh but makes it clear it’s generated at a rate of an average 600W.

      So to be clear a Watt is a unit of power (1Wattr = 1V * 1A in our terms) a WH is a quantity averaged over an hour so 1Wh would be = to 1W generated continuously for an hour. In the same way that 600Wh generated over 2 hours would = 600Wh but be at a rate if 300W\h. So 600W an hour = 600WH (but to the laymen is probably better understood if I had added the word average) and for 10 hours would = 6kwh or 6000WH.

      Of course you’d need more than a 600w solar array, because in general you’ll get about 75% power rating as an average during a summer day.

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