Real world electrical consumption?

[Capt Gary]

I tracked my usage for a couple days trying not to conserve at all. Basically, separate refrigerator and freezer, electric griddle and electric coffee pot running off inverter, lights as if we were plugged into shore power, radio (no TV), shower sump pump (showers for two people) and electric head. Came up with 290 amps per day.

Running one AC zone for 10 hrs adds another 140 amps for a total of 430 amps per day.

However, when cruising, while not giving up many amenities, I live very comfortably on 200 amps/day. (On my old boat with many fewer luxuries, I got by with about 100 amps per day.)

I have a 750 amp/hr battery bank (3-8D's).

[rslifkin]

One thing to consider, particularly if you don't want a generator, is how much solar can you reasonably fit on the boat? And do you also plan to include a wind gen? And how much space / weight can you dedicate to batteries? To a degree, systems design and power usage lifestyle will by dictated by the amount of power you can produce and store.

[a64pilot]

Originally Posted by wingssail

A64, I am just a little confused about how a "suitcase" genset can perform such miracles. Producing 2000watts continuously for a quart of fuel? OK that's 140amps at 14 volts so, OK, it could drive your AC battery charger at 100 amps, considering losses of two or more power conversions. But why is that better than me running my engine for the same time, using .3 gal of diesel per hour and producing roughly 80-100 amps of DC with my Balmar?

That honda must have a marvelous alternator and an excellent regulator and superb cooling for the whole package.

On the other hand, motoring a lot simplifies the problem. Maybe that's it.

Look it up yourself, the Honda 2200 will run from a little over 3 to a little over 8 hours on .95 gls of gas depending on load, my 2000 will do a little better, s it’s a smaller motor and makes 10% less power.
So even at max load the 2200 only uses 1/3 a gallon an hour, my 2000 a little less and 100 amps isn’t quite max load, so about a quart an hour.

Now using my Yanmar 4JHE (44 HP) as an example, in order extract 4 HP from the crankshaft which is about 100 amps, according to Yanmar’s installation manual, I need to be turning 1800 RPM, any less and I’m exceeding the max allowable limit. I choose not to run my motor at 1800 to charge batteries, and I choose not exceed any published engine limitations.
You can argue I guess that Yanmar is wrong, they don’t know what they are talking about but I choose to believe them, it’s readily available information in the engine installation manual.
So instead of running my I guess it’s about a $20,000 engine at 1800 RPM to charge batteries at anchor and burn 1/3 a gallon an hour, I choose to run a $1,000 Honda and burn 1/3 of a gallon of gasoline.

Which way do you think is wiser long term financially?

Oh, and on edit, the Honda is a marvelous little machine, easily making over 13 amps at 120 VAC that is easily with inefficiencies factored in make 100 amps at battery charging voltage levels.
There is only one conversion loss that you see, the first one isn’t counted in for the continuous 13.3 amp output of my little 2000 at 120 VAC.
It will happily make more power, I’ve seen over 16 amps, but it gets loud at those power levels so I don’t let it run that hard.

[Stu Jackson]

Originally Posted by SY Kelpie

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Battery capacity seems to be a function of how much power you use in a day, and whether you want the bank to last you through periods of cloud/rain. But batteries are pretty expensive, compared to solar, so I think we will likely find a balance here which involves relying on engine charging through dull days rather than having an oversized battery bank.

This is a flaw in your logic. That is due to battery chemistry and how batteries actually work. A larger bank is the preferred solution NOT because of period of cloud/rain, but it is because batteries last longer the less they are discharged between each recharge to full cycle.


In addition, many wise skippers on this forum have realized and reported that batteries are consumables, they have a general shelf life and need to be replaced. The larger a battery bank can be for any given daily load, the longer the batteries will last.



I recommend you do some reading at www.marinehowto.com. There is also a ton of material here: Electrical Systems 101 http://c34.org/bbs/index.php/topic,5977.0.html
The Energy Budget topic in that link has calculations for three situations, as Tellie mentioned: anchor, daysail, overnight sail. Large differences in amp hour draws.



There are also some good boat electrical books if you haven't already.


Good luck.

[hpeer]

44’ laying in the Caribbean. Very simple boat
Forgo oat drive freezer is biggest draw.
Mostly foot pumps for water
LED lights
Keep VHF and LED anchor light on 24/7
Older electrical panels has Incandescent indicator lights, they use a surprising amount. Probably our second biggest draw.
Typical battery charging scenario.

2 each 310w solar panels w/ Victron controllers and a wind generator. Honda 2000 gen. 4 GC batteries in series parallel for a 12v Bank. 6 or 8 would be better.

We use about 170aH per day.
The solar and wind generally meets these needs. Rarely have to run engine but happens.

IMHO you take a SWAG at it and see what happens. So much is dependent upon conditions outside your control, or seasonally variable to know for sure. I think if you look at the numbers here you will be in the ball park.

[DMCantor]

The only consumption that really seems to matter is refrigeration. We have both refrigerator and freezer boxes, and together they need about 150 a-hr/day in the tropics. Our next largest consumption is probably the inverter driving chargers for our computers and phones, maybe 20 a-hr/day. We run a 12v watermaker and a washing machine, but that is pure luxury and not something you need.


We find that our navigation electronics and autopilot use surprisingly little, maybe 2-3 amps. We haven't used the autopilot in big seas lately, I'm sure it would be more when its boisterous.

[Pete7]

Originally Posted by SY Kelpie

It would be interesting to hear from people in a vaguely similar situation to see what the actual power requirements tend to be.

Bit smaller and since fitting a 20 litre portable freezer we are probably about 80-100AH per day.

However, what you really need is the at sea figure, so chartplotter, VHF, AIS etc running plus what sort of steering system are you planning on using? wind vane or under deck autopilot, that could be a major current draw.

Pete

[MJH]

Originally Posted by SY Kelpie

I've been trying to estimate our likely electrical power requirements so that I can get on with designing/speccing the system. How long is a piece of string!

We're a 39ft mono with two adults, one child, and we plan to keep it very simple- no watermaker or air-con, but no generator either. Quite happy to use manual water pumps although the boat is currently fitted with a pressurised system. Surely not a big user in the scheme of things.

Current fridge is a Waeco standalone unit, not the best efficiency, I would like to replace this with a built in fridge with water cooling and much better insulation.

Anticipated cruising ground is an Atlantic circuit.

It would be interesting to hear from people in a vaguely similar situation to see what the actual power requirements tend to be.

As everyone will have different lifestyles and equipment onboard you need to make your own Energy Budget. Go to the Pacific Cup website and lookup their Excel template: Pacific Cup 2012 Sample Energy Budget. You can put in all the specifics on your boat including your charging and ask what-if questions to determine what you need...very illuminating.

On my roundtrip to Hawaii I never had to use my diesel to charge the batteries but I have 4x140W solar panels and 2x8D Gel batteries but no genset, no refrigeration, and no watermaker as well...it is amazing what you can live without if you plan right.

~ ~ _/) ~ ~ MJH

[mvweebles]

I put together an XLS spreadsheet to size both solar and alternator - I spent some time looking-up the energy consumption from OEM sites, though estimated a couple too. Mind you, this is for a trawler with 800w of solar so there's energy to spare. Big difference when running vs at anchor - as someone else noted, the A/P takes a bunch, as do the MFDs (e.g. Radar), instrument clusters (mostly still incandescent) etc. Also note there is a separate freezer in the below at about 80AH/day. No fans, which draw a fair amount.

Just depends on how stingy you want to be - whether you run some sort of anchor watch at night, SSB/VHF, etc. At anchor, 125AH-150AH is a reasonable budget. Underway with nav, A/P, etc., could easily quadruple or more.

Just depends on how many switches are in the "ON" mode when you're aboard.

[mvweebles]

Originally Posted by MJH

Go to the Pacific Cup website and lookup their Excel template: Pacific Cup 2012 Sample Energy Budget. You can put in all the specifics on your boat including your charging and ask what-if questions to determine what you need...very illuminating.

Great shout-out MJH. Here's the link. Be aware that energy consumption of devices have improved dramatically since 2012. Newer digital radars are less than half what the old magentron ones were. LED chart plotter displays vs old CRTs. And modern LED lights draw a fraction of what they used to.

Still, I think you have to be realistic on your expectations on how far you will take energy conservation. Running with radar/MFD (and thereby AIS) off for 22-hrs/day seems a bit unrealistic.

That said, very good XLS model to size a system, just need to tweak the values to update for modern equipment.

https://pacificcup.org/node/673

[Brewgyver]

Originally Posted by wingssail

(snippage)
4. Watermaker. Our watermaker is small, it supplies drinking and cooking water, not washing water, it runs 1-1.5 hours per day at 3 amps, so 3-5 AH

Please provide info on this watermaker that runs on less than 50 watts?

[MJH]

Originally Posted by mvweebles

Great shout-out MJH. Here's the link. Be aware that energy consumption of devices have improved dramatically since 2012. Newer digital radars are less than half what the old magentron ones were. LED chart plotter displays vs old CRTs. And modern LED lights draw a fraction of what they used to.

Still, I think you have to be realistic on your expectations on how far you will take energy conservation. Running with radar/MFD (and thereby AIS) off for 22-hrs/day seems a bit unrealistic.

That said, very good XLS model to size a system, just need to tweak the values to update for modern equipment.

https://pacificcup.org/node/673

No doubt about it, you have to research all the electrics on your boat, include their specs, and then make an assumption as to your daily usage. Worked very well for me.

~ ~ _/) ~ ~ MJH

[wingssail]

Originally Posted by Brewgyver

Please provide info on this watermaker that runs on less than 50 watts?

We have a 25 year old Power Survivor 35 (originally a PUR35, now sold by Katydine). It produces 35 gallons per day running full time. So that is about 1.4 gallons per hour. Quite minimal in today's terms, I'm sure you would agree, however it supplies all of our drinking and cooking water, depending on the climate we're in (how much we drink in a day) in about 1-1.5 hours of daily operation. This amount of usage extends our tankage which is 140 gallons. We can go a month without refilling.

The watermaker is running at this moment, it's taking 3-5 amps, average 4amps I guess. That is 48watts. We run it only when the engine is on to ensure it has full voltage available, which preserves the electric motor.

We've replaced the membrane twice in 25 years and have done O'ring rebuilds a couple of times, and some other minor repairs, It's been quite durable and has survived a circumnavigation and 25 years of cruising. We're happy with it's durability.

It's a 12v machine obviously, no frills (no electronics, no pre-filter, no-feed pump), and I can rebuild it in about an hour.

I'd live to have one which makes 5-8 gallons but I don't want to spend the money. When this one fails I think I will build one myself. Others have done so.

[wingssail]

Originally Posted by a64pilot

Look it up yourself, the Honda 2200 will run from a little over 3 to a little over 8 hours on .95 gls of gas depending on load, my 2000 will do a little better, s it’s a smaller motor and makes 10% less power.
So even at max load the 2200 only uses 1/3 a gallon an hour, my 2000 a little less and 100 amps isn’t quite max load, so about a quart an hour.

Now using my Yanmar 4JHE (44 HP) as an example, in order extract 4 HP from the crankshaft which is about 100 amps, according to Yanmar’s installation manual, I need to be turning 1800 RPM, any less and I’m exceeding the max allowable limit. I choose not to run my motor at 1800 to charge batteries, and I choose not exceed any published engine limitations.
You can argue I guess that Yanmar is wrong, they don’t know what they are talking about but I choose to believe them, it’s readily available information in the engine installation manual.
So instead of running my I guess it’s about a $20,000 engine at 1800 RPM to charge batteries at anchor and burn 1/3 a gallon an hour, I choose to run a $1,000 Honda and burn 1/3 of a gallon of gasoline.

Which way do you think is wiser long term financially?

Oh, and on edit, the Honda is a marvelous little machine, easily making over 13 amps at 120 VAC that is easily with inefficiencies factored in make 100 amps at battery charging voltage levels.
There is only one conversion loss that you see, the first one isn’t counted in for the continuous 13.3 amp output of my little 2000 at 120 VAC.
It will happily make more power, I’ve seen over 16 amps, but it gets loud at those power levels so I don’t let it run that hard.

Good analysis, A64. I have no disagreement with any of it. The take away I get it that for roughly the same amount of fuel we get roughly the same amount of energy. I don't think we should quibble about the small differences one way or the other.

The key point you make is that you choose to use the Honda. I choose to run my main engine, at 1800RPM, for an hour a day or slightly more. (I don't disbelieve Yanmar's guidance, please don't patronize me on that, OK?).

We on board Wings are sailors mostly and have a very simple boat and that is not accidental. We like to focus on sailing, not maintaining extra equipment, and not wanting to carry anything along which we don't need. So no genset of any kind, no extra weight, no complexity of a second engine, no extra fuel source, no clutter in the cockpit, no noise from a gas engine sitting on deck. We've done it this way for over 34 years on this boat, over 25 years while cruising, with the same Yanmar 3JH, (now at 6477 hours) and the engine does not seem to have suffered in any way. I am not sure that we've made a financially wrong decision and we certainly have made a simpler cruising boat by forgoing a lot of the stuff that many cruisers seem to prefer, yet we don't think we are inconvenienced in any way. We have our power, our refrigeration, our ice in our drinks. we have our lights, computers, anchor handling equipment...everything. We do however have room for and carry 22 sails when cruising internationally (none on deck and none in the cabin) the dingy is not on deck or on davits and in fact there is nothing on deck and no extra weight aloft.

And we can and have done, 200mile days, two handed.

But it's all about choices, isn't it?

[Tellie]

Originally Posted by DMCantor

We run a 12v watermaker and a washing machine, but that is pure luxury and not something you need.

You should hear the calls I have been getting for the past weeks. There are a lot of people stuck unable to go onshore all over the world and are finding that watermakers and washing machines are not so much a luxury right now.


PS " but that is pure luxury and not something you need." You don't "need" a boat either.