Real-Life Power Consumption Numbers

[sailjumanji]

There have been several threads started recently regarding how much solar or batteries are required for cruising. For most, the answers need to start with the boaters assessment of how much power they are going to use. As such, I thought I would post up some of the numbers from our set-up. We have a Seawind catamaran that has two 120 watt solar panels on an arch, three Deka 105 amp-hr AGM batteries, and a Blue Sky MPPT controller. The controller also has a readout showing how many amps are coming from the solar panels, as well as a shunt to show how many amps are being consumed (coming from batteries). I took some measurements one night - when the solar panels obviously are dead - turning instruments on and off, and recording the change in amps consumed. Note that we have optimized a lot on our boat to keep our power consumption to the point of not needing a generator. We carried a Honda 2000 as a backup on our three-month trip to Bahamas, but only used it once - when I forgot and left the watermaker on while sailing long passage on a very overcast day!

Big power users:

Fresh water pump - 8.6 amps. I think this is a 3.5 gpm pump on a pressurized water system. It kicks in when a tap is open, including shower. So limited run time.

Spectra 150D watermaker - 8 amps. We only run this in the middle of the day, when power consumption can be covered by solar panels. In full sun, we get about 7-7.5 gph.

ICEER refrigerator/freezer. Draws 4.6 amps when cooling. (0 when on standby)

Autopilot. This one is tough to measure, as it depends on how hard the autopilot has to work to keep the boat on course. My guess is that when it is steering hard, it draws up to around 5 amps. This really becomes an issue on overnight passagemaking.

Instruments and lights:

Fluorescent lights. We have several of these interior lights - 2 bulb, 12". They each draw 0.7-0.8 amps each. We avoid using these for long periods.

Alpenglow LED reading and overhead lights - 0.2 amps each. These are low power draw - compared to the fluorescent - and put out much more light as well.

Stecktronics tricolor LED nav light - 0.2 amps. On top of mast. In the anchor light mode - draws 0.1 amps. This was a huge power savings vs the standard bulb anchor and nav lights.

Caframo fans - draw 0.3 amps on low, 0.5 amps on high. These are the old style that don't have any cage covering the fan blades.

Fusion XM radio (stereo) - 1 amp. During overnight passages, we listen to XM news channels, etc. to help keep awake.

Autohelm ST60 Wind and Depth/Speed instruments, Vesper AIS & splitter - 0.4 amps. Sorry I don't know the split, as these are all on one switch, but each have a fuse on the bus.

B&G Zeus 2, 9 inch touchscreen chartplotter and GPS - 0.8 amps.

B&G 4G radar - 1.5 amps on transmit, 0.3 amps on standby. One of the reasons we went with this radar unit was low power consumption, as well as very detailed scan.

Icom VHF radio - 0.4 amps on standby.

With all instruments and lights off, we draw about 0.4 amps. That's from radio memory, battery pulsers, and who knows what else.

Overnight sailing - from memory - our draw is 8-9 amps. What we can measure easily is 4.7 amps, that includes XM radio (1 amp), VHF (0.4 amps, standby), instruments (0.4 amps), chartplotter (0.8 amps), radar (1.5 amps transmit), nav lights (0.2 amps), and 0.4 amps background. If the fridge runs one-third of the time, that is another 1.5 amps effectively - now total is 6.2 amps. Autopilot is unknown, but if we are drawing around 8-9 amps with everything, that would put the autopilot at 2-3 amps effectively. If you are doing this for twelve hours, that's 96-108 amp-hours of battery used up. So for us, that is 34% of our three-battery capacity. This scenario is the hardest draw on the battery bank.

You can obviously save a bit of power by turning off the XM radio (1 amp), and turning the radar off and on to effectively run it half of the time (saves 0.7 amps).

Overnight on anchor, we generally use about 25-35 amp-hours. That's from washing dishes, showers, refrigeration running, some lighting, and portable DVD player. On a sunny day, the solar panels will make that up fully by around noon-time. Then in the middle of the day, we run the watermaker. That puts an 8-9 amp load on the system, which the solar panels cover almost directly - leaving the batteries still at full charge. (Or at least that is the way it appears to be working, as the batteries are registering around 13 volts).

Looking at the numbers, I would probably be better off by adding another battery to the system. As it is, I have a two-battery "house" bank, and a single battery "engine" battery. Most times though, I set the battery switch to "both", so on events like overnight passages, I do not draw ~100 amp-hrs off of a two-battery 210 amp-hr bank, but instead draw off the "both" 315 amp-hrs. If things really go bad and don't have enough power left to start the outboards, both of my 9.9 hp motors are pull start as well as electric start. But as overnight pure-sailing passages are not typical, I have not run into any issue yet. We try to do most of our sailing during the day.

When we are motoring long distances with both of the motors, we usually turn on lights, fans, stereo, charge ipads, etc, to get power usage up, and prevent the small alternators on the motors from overcharging the batteries.

Note that we do not use a large inverter. We have a very small one that we use to charge up camera batteries, but that's about it. Nor do we have a computer onboard. We carry an ipad for wifi use in port, as well as backup chartplotter. We don't have a microwave either. Our stove, barbeque pit and hot water heater are all propane. One 10-lb tank lasted us two months.

[a64pilot]

Contrast that with I use at least 5 times as much power, to some extent because I can.
That may sound silly but I usually don't watch power consumption and we do have a KVH TV5 and a decent sized TV, a large and not well insulated fridge/ freezer that takes a BD80 sized compressor to run it, and we run CPAP machines all night.
I have not cruised for extended periods this is from weekends and a few weeks or cruising, and I am building an electrical system that will hopefully handle all the loads, so we are not being miserly.
I think power is like water, if you have an unlimited supply, you will waste a lot of it.
If not then you will adapt to some extent to what you have.
I always have my selector switch to Both, I can't get it around my head that I need two banks. I think I can manage one just like I have one fuel tank.
I have a large inverter a Magnum MS 2812 and we leave it on always, and toast bread for sandwiches or whatever

[sailjumanji]

Originally Posted by a64pilot

Contrast that with I use at least 5 times as much power, to some extent because I can. .....

I think power is like water, if you have an unlimited supply, you will waste a lot of it.
If not then you will adapt to some extent to what you have.

Yeah, we use water like we have an unlimited supply - because essentially with the watermaker, we do. In the Bahamas, we made enough that we would wash down winches and other things, take showers after swimming, etc.

I forgot to mention that we do run a Honda 2000 generator when we use the air conditioning (8500 btu, in the port "sleeping" hull). But Bahamas were nice enough that we never needed it, and even Florida in March was pleasant. Texas in July or August is another matter!

[ranger58sb]

Originally Posted by sailjumanji

There have been several threads started recently regarding how much solar or batteries are required for cruising. For most, the answers need to start with the boaters assessment of how much power they are going to use. As such, I thought I would post up some of the numbers from our set-up.

It's very likely the extensive numbers you've posted will help many...

But I'll offer an other approach: determine what features you want in a boat (including electrical stuff), buy a boat with those features, use as many batteries as will fit in the logical space available, and then modify your behavior if necessary to live within the power limits available.

Example: A buyer might want a fridge (or two), AC (or two), water heater, electronics... freshwater, interior and exterior (including nav) lighting... and it's often sometimes easier to solve all that during the shopping phase rather than afterwards. Buy the boat, add batteries if necessary and possible, maybe improve some features as possible (change out incandescents lights to LEDs, etc.), use the boat.

If that means genset running while underway, so be it. Or maybe running once/day, OK. Or maybe once/week, fine. Or maybe add solar or wind generator. Or maybe don't turn on electronics when not strictly necessary. Or bag the fans, open the portlights. And so forth.

IOW, instead of developing angst over every little milliwatt, enjoy the boat.

I realize that when folks already have the boat but not all the features desired... sometimes it takes some study to decide whether one could get there from here via improvements to that specific boat. At that point, of course actual factoids can be useful to determine feasibility/viability... but if there's a decision to go ahead with a particular project (e.g., add batteries, add an autopilot)... it's fairly easy to revert to a "don't bother with the minor details" attitude.

I don't intend this as a critique of approaches; just mentioning that every little milliamp isn't all that important to boatloads (?) of boaters.

-Chris

[Typhoon]

a large and not well insulated fridge/ freezer that takes a BD80 sized compressor to run it, and we run CPAP machines all night.
I have not cruised for extended periods this is from weekends and a few weeks or

Hey Pilot ,I thought you were coming up here for me to fix that power hog of yours .

Regards John Tully

[a64pilot]

Originally Posted by ColdEh Marine

a large and not well insulated fridge/ freezer that takes a BD80 sized compressor to run it, and we run CPAP machines all night.
I have not cruised for extended periods this is from weekends and a few weeks or

Hey Pilot ,I thought you were coming up here for me to fix that power hog of yours .

Regards John Tully

It's insulation, or lack of it that is the power hog in the fridge as well as its I think 14 cu ft. It is a rather efficient system, just the lack of efficient insulation and size is the issue.
I chose, knowingly and intentionally to solve my dilemma with an oversized dual cold plate system as I was unwilling to tear the boat apart and increase insulation.
For me it was far easier to add another Solar panel or two than it was to gut the insides of the boat, cause for one thing, projects grow. Once you rip out the counter top and cabinetry, then the desire to go to a bigger sink, custom cabinets, granite counter tops etc kicks in, and you have to do the heads then too to make things match.
I have a name for that in designing / building aircraft, I call it "creeping elegance". You have to be very careful to keep from blowing the budget and actually finishing any where near on time. I will likely add some insulation to the interior thereby decreasing the size some and of course cutting way down on compressor run time.

I have other pressing issues to solve first, driveshaft vibration, new standing rigging / chain plates, new Bimini etc. , new Settee cushions, new mattress in our bed, upgrade interior lighting, and install a watermaker.
Then I will circle back and clean up some nice to do projects like the fridge insulation.

Besides I think its Skip that needs your help, his fridge ate his battery bank

On edit, I chose what I believe Ranger42 is saying, I stuffed in as many batteries as I could fit, as much Solar as I could fit, installed a built in Diesel genset and a decent alternator with three stage regulator.
I may hopefully have more Solar and bank than I need. That remains to be discovered, if not then we will adapt and run the generator more or learn to conserve.
I believe we have to actually be out there for awhile to see, until then it's like planning a monetary budget, you should plan, but until you get out there, its all theory

[Typhoon]

Lol ��. Sorry I mentioned it . You have a lot to do. I know Skips got a real mistery there , he may be best served to pull all his gear and star over . Gremlins . Hey , no need to pull the cabinetry , I have done over a dozen boxes now, right through the hole . Ok that sounds a little strange, but you know what I mean . A cut off saw is your best friend . But you do have to build a new liner . I will be posting a new video with narration by my wife , she is so good at that , I get way to technical, On my website blog in the next week .

Regards John Tully

[Stu Jackson]

Originally Posted by ranger42c

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IOW, instead of developing angst over every little milliwatt, enjoy the boat........................

... sometimes it takes some study to decide whether one could get there from here via improvements to that specific boat. At that point, of course actual factoids can be useful to determine feasibility/viability... .....................
..........................

I don't intend this as a critique of approaches; just mentioning that every little milliamp isn't all that important to boatloads (?) of boaters.

-Chris

Very good advice, Chris.

To the OP, you're kinda reinventing the wheel.

Sure, do an energy budget with all your bells & whistles, and then read these, which I wrote years & years ago. What Chris and others have said is so very true.

Your boat, your choice.

***********************

The All-Important Energy Budget:
Energy Budget

Record of Daily Energy Use of 100 ah per day:

"Breaking In" New Wet Cell Batteries

Largest House Bank 101 (by Nigel Calder)

Calder battery sizing & stereo-battery connection

[StuM]

Sailjumanji, excellent information.

I suspect that you are definitely on the frugal end of the energy usage scale, especially for cat owners who have the luxury of more real estate for solar installations

[VERSO I]

Thanks Sailjumanji! I appreciate the fresh numbers from someone with modern equipment. I'm a new sailboat owner, and I originally found your post because I was looking for numbers on routine power draw for fridge/freezer compressors. Could you tell me if the 4.6 amps quoted above for your system includes one or two compressors? I know basically nothing about these systems, would you suggest this is a typical power draw for the number of compressors you run?

[barnakiel]

There is at least one alternative take: make as much as you can, from as many sources as you can. For you can always consume less than you make, never more.

Take an average 40 footer (say a Lagoon 40'), give it 1kW of solar, 2x 400W windgens and a genset. Then simply switch of the plasma when you see the voltage drop below 12 Volt.

There are many ways to skin a cat or a mono.

Cheers,
b.

[sailjumanji]

To be quite honest, other than vacuuming the vent, I have never looked into how the ICEER freezer/fridge operates. I suspect it has a compressor, and at it is a relatively small plate as separate fridge and freeze compartments, it can't have more than one compressor.

[daletournier]

Its the extented passages that eat up the power, it compounds. Trying to get the bank back up is difficult with power hogs like the autopilot. I tend to start the engine each morning to whack a big chunk in while underway.
A64, I also have always struggled with having a perfectly good battery sitting there doing nothing and combine both banks regularly, when in a area that assures me I don't be stuck, obviously the danger is the whole bank going down and not having a way to start the engine, what is your plan regarding this?

Sent from my vivo Y35 using Cruisers Sailing Forum mobile app

[Typhoon]

Our boat has been on ships power since we dropped in the lithium bank . We are plugged into shore power but it is only connected to two small space heaters . We don't charge our batteries with a charger , only the generator and no solar . We charge for two hours every week . We have all the ships systems running off the batteries that includes two refrigeration systems , a separate deep freeze and refrigerator . Tv lights furnace for hot water and pumps . All in , 400 amp hrs a week . This is at the dock or on the hook , same .

Regards John

[Scot McPherson]

Originally Posted by a64pilot

I have a name for that in designing / building aircraft, I call it "creeping elegance". You have to be very careful to keep from blowing the budget and actually finishing any where near on time.

There is actually an industry standard term for this...it's call gold-plating...When you gold-plate a project, you are going way overboard where it's clearly not needed.

Sometimes gold plating is used in one part of a project to take attention away from a failure some place else, so as the customer when you see gold plating going on, be sure you look under the surface.