So I was trying to figure out how much power items at my house use. I have a standard looking power meter outside with the dial http://en.wikipedia.org/wiki/File:Electrical_meter.jpg" [Broken]. I am trying to figure out though what unit the meter uses. My first instinct was watt hour, but I can't get the numbers to match. The dial has numbers on it 0 - 90, so a full rotation is 100 units of something. It takes about 40 seconds to make a full rotation mostly everything off (like if we weren't home), and 16 seconds to make a rotation with a lot of stuff on. That works out to 90 and 225 rotations per hour. This should give a nice lower and upper bound. Last month our bill was 696 kWh, which works out to 967 watts on average. If I assume one rotation is 100 watt hours then the monthly usage would work out to 6,480 kWh and 16,200 kWh, way too high. My next thought was that a full rotation was only one Wh. This would give us 64.8 kWh and 162 kWh, way too low. It seems be off by a factor of 6. Then I thought the meter said 240v, so it probably meters at 240 volts, if the meter did 240 volts and bill was in 120 volts that still wouldn't be right, plus I think that's pretty unlikely. I also noticed the meter says 240v 3W, so if each turn was 3Wh at 240v, and the bill was in Wh at 120v that would actually work out, but that's a pretty big stretch. So, does anyone know how the dial on the meter measures usage?