Why does my microwave use a lot more power than advertised?

Old 05-15-17, 07:56 PM
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Why does my microwave use a lot more power than advertised?

I have a panasonic NN-H624BF microwave from 2004. In addition to looking up specs in the owners manuals, I'm trying to get real world numbers for how much energy things use in my home.

The owners manual from panasonic.com says cooking power 1250w, and actual power consumption 1460w, 12.7Amps. The microwave uses "inverter" technology if that makes a difference.

When using the microwave with a kill-a-watt meter hooked up, the meter started beeping, and said 2020watts, and 17.1Amps.

Any ideas why this might be...?

I have no plans to run the microwave with a generator hooked up, but the reason why I'm doing this is so that I can get an idea on how much energy things use in case I do decide to run them with my new inverter generators.

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Old 05-15-17, 10:24 PM
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I'd verify with a clamp on amp meter.
Old 05-16-17, 03:53 AM
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You should expect some losses when producing the energy to cook.
The 1475 watts you are seeing is in line with the 12.7 amps the specs say the oven draws.
Old 05-16-17, 05:56 AM
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While the microwaves may be very efficient at heating food, producing them is not as efficient. The magnetron that generates the microwaves generates a good bit of heat (wasted energy) and must be cooled by a fan. Then there is the motor turning the turn table and also the light. I have read that a microwave is only about 40% efficient at boiling water.

Here is an article that goes into detail about various ways to heat water and their efficiency. If you don't want to read the whole thing there is a table half way down that summarizes how efficient different methods are at heating water.

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