How many kilowatts per day do you use?

[accomplice]

58 foot boat. Usage depends.
10kW genset, 250w solar, 150amp (24v) alternator


Refrigeration usage depends on air and water temp and whether freezer is on. Range is 700Wh/day to 3kw/ day.

Nav electronics and autopilot are 3kWh to 5kWh depending on radar use, sea state etc. this is obviously only while underway


A/c is huge load, but not often used. With all 5 zones on, can be be up to 100kWh/day


Washer and dishwasher are significant when running, but usage is sparse and irregular. Same with water maker. Comfortable usage is 10 gal/day/person (yes, one can get by with much less). 39 gal/hour at about 4kW, so 1kWhr/day/person? All of these and a/c only run from genset or, occasionally, shore power.

Ice maker is about 500W when running, but duty cycle depends on ambient temp and how much is in it, how many times opened. Probably averages 10-15kW/day if using it.

Other electrical (lights, communication, entertainment, ventilation, small appliances), vary but typically 2-3kWh/day.

The boat is in the Caribbean during winter, New England during summer.




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[Raythesailor]

Hi
We live on board a Jenneau45 for 6/7 months in Greece. We were having battery problems until;

We had two 100 watt solar panels fitted and have never looked back. We can live on the hook indefinitely with the fridge permanently on. Watch TV and DVDs via an investor and charge, laptops and leave the anchor light on all night

When sailing all instruments are powered up, we even have radar(but don't leave on all the time.)

Solar panels for long term cruissing I think are essential. They must be mounted with as little or no shadow for full efficiency.

[Lepke]

I'm 67 and like my comforts now. About 30kwh/mo winter and 20kwh/mo summer. I have house sized appliances, double door refer, washer & dryer, dishwasher, etc. Primary heat is pellet stove, but have diesel/hydronic and electric space heaters for backup. I don't go where I would need AC.

[TheThunderbird]

I am sorry to say that the STUM's explanation to some high-IQ readers didn't hold true!


When people say consumption is xxxW "per day" they already factor in TIME on a 24h basis.

And that is exactly power x time = consumption
With a 25W bulb ON for 24h, consumption will be 25W x 24h=600 Wh cumulative ON A DAILY BASIS

Power is instantaneous measure, consumption (work, energy) is over time
Happy all?

[valhalla360]

Originally Posted by TheThunderbird

I am sorry to say that to STUM's explanation to some high-IQ readers didn't hold true
When people say consumption is xxxW "per day" they already factor in TIME on a 24h basis.

And that is exactly power x time = consumption
With a 25W bulb ON for 24h, consumption will be 25W x 24h=600 Wh ON A DAILY BASIS

Power is instantaneous measure, consumption (work, energy) is over time
Happy all?

"per" is equivalent to "divided by" at least mathematically. Your 25W bulb would theoretically start drawing some wattage and gradually increase it's draw by 25W per day. So if it started drawing 10W, after a day it would be drawing 35W.

In your example, you were showing 25W-days is equal to 600W-hrs. (the "-" is equivalent to multiplication in common engineering parlance)

Stu' explanation is correct.

[TheThunderbird]

@Valhalla
I agree with STUM in full, it doesn't hold true to some others... not me!

I don't agree with others who argumented with me, and him too :-).
..

Btw I don't follow your bulb example... :-) (?!?)

[valhalla360]

Originally Posted by TheThunderbird

@Valhalla
I agree with STUM in full, it doesn't hold true to some others... not me!

I don't agree with others who argumented with me, and him too :-).
..

Btw I don't follow your bulb example... :-) (?!?)

In reality it doesn't work for a bulb but....

Watts per Day (aka Watts/Day) is a rate of change in watt draw. It really doesn't have a practical application but you could consider it like a dimmer (though that isn't quite how a dimmer and blub works). Assuming the dimmer wastes no electricity, you could start it with a lower setting of say 10watts and if you have a 25W/Day rate of change, after 1/2 Day, the bulb will be drawing 22.25W (10 + 25/2).

There is no practical use for this calculation when talking about light bulbs on boats.

[OneLeggedParrot]

Originally Posted by AFKASAP

...How much electricity do you use per day while living aboard...?

1. 34' monohull in the past
2. Mostly laptops and LED lights and a recharger for the older headlamps and lights that use AA/AAA's (when we are tied to a dock we wind up using TONS more; R/F, Coffee Makers, Toasters, careless about lights on, etc.)! We used a wood stove for heat, no AC (sometimes a little fan in summer though) so not a factor when it's cold or hot -seasons fairly irrelevant
3. There's other seasons besides Rain and Mist?

I never measured it, but even with cloudy days, we managed to keep things topped off with a decent 250w-300w solar system off a few 100aH deep cells, just using laptops for work all day (low drain more modern ones though), LED lights at night in the boat and headlamps if we need them, and the chargers for the AA/AAA stuff -use the laptops for nav and GPS and didn't have radar and rarely used it when we did. Sometimes we'd run the engine to charge the batteries if the cloud cover didn't break up often enough for a week- but a good system will still charge even with some cloud cover.

I agree with a good solar system is essential. There's usually lots of sun where there's water, at some point- and not so many trees or buildings where there's boats. Usually.

[AFKASAP]

Originally Posted by Raythesailor

Hi
We live on board a Jenneau45 for 6/7 months in Greece. We were having battery problems until;

We had two 100 watt solar panels fitted and have never looked back. We can live on the hook indefinitely with the fridge permanently on. Watch TV and DVDs via an investor and charge, laptops and leave the anchor light on all night

When sailing all instruments are powered up, we even have radar(but don't leave on all the time.)

Solar panels for long term cruissing I think are essential. They must be mounted with as little or no shadow for full efficiency.

Hi, where are they mounted? Can you tilt them or are they fixed? What controller do you have? Also what batteries do you have? Cheers

Beneteau Oceanis 40 - 2008
Mallorca

[OneLeggedParrot]

Originally Posted by AFKASAP

Hi, where are they mounted? Can you tilt them or are they fixed? ...

Hey, check this out.
Goggle result
& (what I was trying to find with that google search)
Going Solar | Cruising World

That's a really nifty way to do things if you're not going into heavy weather. If you do a lot of heavy weather or blue-water voyaging, mounting your solar in the back up high is pretty common.

We had two places on our boat- back aft like typical and a 2nd location I could move the panels on front of the mast, for when we were in northern latitudes sailing south.

I'd say the most important part of the solar system that gets overlooked is the charge controller -get a good MPPT that won't interfere with other systems or create too much RFI!

[Lantau]

The big draw comes when on passage when most everything you need is operating. I had a big shock (a nice one) recently after replacing our chartplotter and radar scanner: the power consumption by those to things, which was considerable with the old radar operating, dropped to almost nothing with the new radar, and the new plotter uses virtually nothing. Now, even if sailing at night with the radar on all the time, and the Monitor windvane doing the steering, we can get by on solar and wind power. The message is that if you have older electronics, at least the stuff that draws significant power (old displays, radar scanners, etc.), it may be worth replacing them if you want to reduce power consumption.

[AFKASAP]

Can someone please explain something to me.

I have two 140 AH batteries for services. So that's a total of 280 AH. So if they are 100% charged, how long can I run my fridge for assuming I do not want to drain more than 50%. So that gives me 140 AH of usable power.

When the fridge compressor kicks in it says 5A on my battery panel display.


Beneteau Oceanis 40 - 2008
Mallorca

[newhaul]

Originally Posted by AFKASAP

Can someone please explain something to me.

I have two 140 AH batteries for services. So that's a total of 280 AH. So if they are 100% charged, how long can I run my fridge for assuming I do not want to drain more than 50%. So that gives me 140 AH of usable power.

When the fridge compressor kicks in it says 5A on my battery panel display.


Beneteau Oceanis 40 - 2008
Mallorca

If I understand you correctly you would be able to run the compressor for 28 hours.
5ah draw x 28 hours = 140 ah. The part you need to know is what is the cyclic of your refrigeration system is. On our Spence sailboat. The refer used about 4 ah with about 5 hours of operation per day. For a daily consumption of 4 ah x5 hours = 20 ah per day usage .

How do you charge on a daily basis?

[StuM]

As Newhaul says, it depends on how long the fridge compressor runs each hour. During the day when it is hotter and you are opening the fridge more frequently, it will use more Amp Hours in an hour than it does in the middle of the night.

A lot depends on your usage pattern, the ambient temperature and how well your fridge is insulated. You really need to measure it in your typical conditions.

That said, Newhaul's 5 hours total runtime over a 24 hour period is not unreasonable. Possibly a safe estimate would be running 25% of the time so that would give you 5 x 24 x .25 = 30Ah per day. Meaning that if there are no other loads, your 140Ah available is good for 4-5 days.

If the boat is unattended so no one is opening the fridge and putting warm beers in it, it should be good for a week

[AFKASAP]

Thanks guys. I think I understand that now.

Beneteau Oceanis 40 - 2008
Mallorca