I see a lot of people here use the killawatt meter which is nice for 120vac plug in items but some want to measure the usage of 220/240 equipment. Heres a quick way to calculate your electric meter usage with a stop watch or anything with a second hand.
The way I do it is to unplug my refrigerator and any other appliance that starts automatically and turn the breaker off to the water heater, you don't have to unplug everything just have them turned off, I prefer this method over unplugging everything because it gives me my minimum usage of all clocks, wall transformers, and standby current of TVs and VCRs etc.
1) first find your meter code on the front dial - something like Kh7.2
2) with everything done as outlined above time the black mark on the disc for one revolution
3) take the seconds in step 2 and divide by 3600 (converts the number into hours)
4) take the number in step 1 and divide by the hours in step 3
5) that is the watt hours usage
an example of my house with everything off:
my meter is a Kh7.2 and took 175 seconds to go around once from black mark to black mark
I divide 175 by 3600 and get 0.0486 hours
then divide 7.2 by 0.0486 and the result is 148 watt hours
148 watts is what I call my quiescent power, and at my rate of 10 cents is about $11 a month with nothing actually running
I subtract it from all other readings - here is the big burner on my stove top
10 seconds for one revolution divided by 3600 equals 0.00277 hours
7.2 divided by 0.00277 equals 2600 watts total house draw
2600 minus 148 equals 2452 watts for the burner element per hour
2.45 kilowatts times 10 cents (my cost) equals about two bits an hour to run
It makes no sense to do your refrigerator and water heater with this method because of the variables, water heaters on average will cost 50 cents an hour to run at full recovery but only your actual hot water usage can determine that.
If you are going to measure a window or central air conditioner you must take multiple readings over a fair amount of time because the way the compressor and refrigerant cycle works with head pressure and temperatures - an ac will likely run quite a few watts less when first turned on and will slowly creep up with time. My little window unit, 5000btu with a nameplate rating of 4.9 amps only draws 2.6 amps (300watts) at first then slowly climbs and within 15 minutes it is at 3.8 amps (460watts). The nameplate says 530watts but would probably not get there until the outside temperature reaches the maximum design for the unit or about 95 degrees and inside temp is fairly warm.
Hope I made it clear enough for some of you to use.
The way I do it is to unplug my refrigerator and any other appliance that starts automatically and turn the breaker off to the water heater, you don't have to unplug everything just have them turned off, I prefer this method over unplugging everything because it gives me my minimum usage of all clocks, wall transformers, and standby current of TVs and VCRs etc.
1) first find your meter code on the front dial - something like Kh7.2
2) with everything done as outlined above time the black mark on the disc for one revolution
3) take the seconds in step 2 and divide by 3600 (converts the number into hours)
4) take the number in step 1 and divide by the hours in step 3
5) that is the watt hours usage
an example of my house with everything off:
my meter is a Kh7.2 and took 175 seconds to go around once from black mark to black mark
I divide 175 by 3600 and get 0.0486 hours
then divide 7.2 by 0.0486 and the result is 148 watt hours
148 watts is what I call my quiescent power, and at my rate of 10 cents is about $11 a month with nothing actually running
I subtract it from all other readings - here is the big burner on my stove top
10 seconds for one revolution divided by 3600 equals 0.00277 hours
7.2 divided by 0.00277 equals 2600 watts total house draw
2600 minus 148 equals 2452 watts for the burner element per hour
2.45 kilowatts times 10 cents (my cost) equals about two bits an hour to run
It makes no sense to do your refrigerator and water heater with this method because of the variables, water heaters on average will cost 50 cents an hour to run at full recovery but only your actual hot water usage can determine that.
If you are going to measure a window or central air conditioner you must take multiple readings over a fair amount of time because the way the compressor and refrigerant cycle works with head pressure and temperatures - an ac will likely run quite a few watts less when first turned on and will slowly creep up with time. My little window unit, 5000btu with a nameplate rating of 4.9 amps only draws 2.6 amps (300watts) at first then slowly climbs and within 15 minutes it is at 3.8 amps (460watts). The nameplate says 530watts but would probably not get there until the outside temperature reaches the maximum design for the unit or about 95 degrees and inside temp is fairly warm.
Hope I made it clear enough for some of you to use.
