Measuring KWH on major appliances.

mryimmers · July 2016

Hi all,
I am planning to build a new house in the not too distant future and am considering the possibility of keeping it off grid.
We are currently "on grid" and all of our major appliances are electric. This includes clothes dryer, hot water heater, cook top and oven. We have a pretty good handle on our usage, and I would like to use our history to help in planning an off grid system.
My question is how do I measure the KWH used by the above mentioned appliances so that I can remove that amount from my daily required KWH? All those appliances would be propane fired in the off-grid build. Home heating is wood, with propane back-up.
Is there a clamp-on amp-meter that can measure KWH over time? Then I could just put it on any of those appliances for a 1 or 2 months at a time and get a pretty accurate idea of how many KWH each one uses, and take that amount off of our current usage, which is in the 24-30 KWH per day range, then I would be left with a number that should be pretty close to what would be required for a system. thanks hh

Wheelman55 · July 2016

For $30 you can get a P3 Kill-a-Watt meter.

http://www.p3international.com/products/p4400.html

Be aware that it will only measure 120v and a max of 15 amps.

You will also need to know the surge amps on each appliance in order to calculate true needs for solar. Enjoy the journey.

jonr · July 2016

For 240V and more amps, search ebay for "100A AC digital KWh watt meter". Could be installed at your panel.

BB. · July 2016

I don't remember where you are located... But, if you are around Lake Superior, what are you going to do in winter when you have something like 2-3 hours of sun per day in the winter. Going to go with genset/wind turbines?

30,000 WH per day * 1/0.52 typical off system eff * 1/2.5 hours of sun (winter) = 23,077 Watt array nominal
30,000 WH per day * 1/0.85 inverter eff * 2 days of storage * 1/0.50 max discharge * 1/48 volt battery = 2,941 AH @ 48 volt battery bank
2,941 AH * 59 volts charging * 1/0.80 charger eff * 1/0.80 genset derating * 0.10 rate of charge = 27,112 VA rated genset minimum

That is a quick estimate of what you would be looking at if you want to continue to use 30 kWH per day in winter.

For measuring larger electric appliance usage--You can get whole house monitoring systems like this (some models can measure several specific circuit energy consumption at the same time).

http://theenergydetective.com/

-Bill

mryimmers · July 2016

I have a kill-a -watt meter, very handy tool!! But I want to determine what my major appliances are using and be able to subtract that off of the 24-30 KWH that I use now, but being that they are all hard-wired in it isn't so simple as plugging in the kill-a-watt.
I don't intend to need anywhere near 30 KWH per day if off grid. I was guessing more like 5ish, but I don't want to guess. I'll check those suggestions, I suppose it will require wiring something into the circuits I wish to check. I am in Thunder Bay Ontario. Thanks guys!!

BB. · July 2016

The Energy Detective--Uses a CT (current transformer). You open your main breaker panel and clip a CT on the lead you want to measure power on. Can do the mains, and/or branch circuits.

-Bill

mryimmers · July 2016

Checking that out, thanks Bill!!

mike95490 · July 2016

24-30KWh daily is going to require a large system. 2 people, 3 fridges and 3 hours of water pumping and I do 12KWh a day in the summer, and just 7 in the winter. wood and propane heat, propane dryer, front load washer, Bosch dishwasher and B&D electric toaster.

BEWARE the gas heating appliances, often the oven and clothes drier have a "glow coil" ignition system that uses 400W to ignite and 200w to monitor the presence of the flame

Measuring KWH on major appliances.

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