DIYbanter - View Single Post - Estimating KWh electicity billing using clamp-on amp meter

Ralph Mowery

In article , says...

Would be interesting to learn how to do it with a
garden-variety clamp meter with unknown transfer
function for loads with non-unity power factor and two load
branches with different loads.

You can not do that with simple meters.

I have one meter that reads volts, amps, watts. With resitive loads
like light bulbs and heater elements without blowers the volts times
amps give the same value as the watt scale. If I hook up something with
very much inductance such as a motor or even a heater with a blower, the
volts times amps are way off from the watt meter.