how to measure the power of home electric machines?

Answer 1

You can measure the current and voltage and calculate the power using watts = volts X amps. With motors and some other equipment, this will only be an estimate because it neglects power factor. You can buy a plug-in wattmeter (available for USA) called kill-a-watt for about $20.

Answer 2

to get an actual measurement, not just the manufacterers claims which can be very inaccurate, you can get a clamp on ammeter from Radio Shack or most any electrical supply store. since the voltage supplied to household appliances is constant, that has to be measured only once, or for approximations, an estimate of 120 volts is adequate. The power that you pay for is the amps measured by the meter times 0.12 to give kilowatts. multiply that by the hours of operation to get KWH which is what the utility company charges you for.

one thing that you will notice is appliances like microwave ovens and refrigerators do not run continuously, and the amp draw varies when in operation. also this measurement is the power consumed by the appliance (what you pay for) and not the energy delivered for the job. That depends on efficiency of operation. comparing the power taken by different brands of equipment to do the same job can be quite enlightening.

Answer 3

To measure it requires a power meter, these can be bought fairly cheap (Kill A Watt) that plug straight into your appliance. Don't try to use an ammeter, without going into detail, it doesn't work.

You can estimate from the numbers on the power rating but, depending on the appliance, these are maximums and power may not be constant such as refrigerators so numbers based on these can become inaccurate.

Answer 4

Check the appliance ...
It must have a value with units "Watts" o abbreviated as "W"
... thats the power rating of that machine.
Simple :-)
Or go for the hassles of finding out the other way...