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Your microwave is wasting money

18 November 2009 2,153 views No Comment
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When I first thought up this experiment, I didn’t have too much optimism. I thought this would be a boring article to write. After all, the energy consumption sticker / UL rating at the back of my microwave read 1.2kW, which translates to 1200 watts. It’s a typical, mid size microwave oven.

Obviously, having studied home energy usage and trends, I know the microwave used energy when I wasn’t using it. The little LED on the front that conveniently showed me the time didn’t come at no cost. But I didn’t actually know how much.

Tonight I was curious enough to find out. And I found out a few more things along the way.


Here’s the energy consumption of my microwave oven at typical “phases” of the usage cycle.

  • Standby – 4 watts. Therefore, the microwave always uses this amount of energy unless it is unplugged.
  • Door Open – 24 watts. The light bulb, when turned on, draws 24 watts of power. Add this to the 4 watts that is “always there” and you have 28 watts.
  • Full “Duty” or Heating Cycle – 1280 watts. So much for the 1200 watt sticker. If we subtract the energy cost of the standby/LED, the light bulb that is turned on, the fan and the motor to turn the plate, we get about 1200 watts. Eureka!
  • End cycle (no microwave radiation) – 70 watts. This energy cost of the motor, fan, LED, and light.

So what does it mean?

It means the 1200 watts you’re thinking your microwave is using is actually only the energy cost of the microwave/radiation generating unit itself. This component draws the wattage advertised. The actual unit itself draws more, possibly 100 watts more during full cycle. You have to take this into account when figuring out your energy usage and not take the energy rating of a microwave at face value only.

The power level doesn’t matter.

Armed with this evidence, I decided to extend the experiment. What if I decreased the power from 100% to 50%? Would I see a decrease in power consumption from the unit?

  • At full 100% power, the microwave drew 1282 watts of power.
  • At 50% power, the microwave drew 1280 watts of power.
  • At 75% power, the microwave drew 1283 watts of power.

According to this study, the power level doesn’t seem to affect the power consumption at all. The unit draws the same energy whether being used at 50% or 100% power. Therefore, given the choice, use the unit at 100% power because it will cook/do the job faster and use less energy.

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