I know CogDaily is supposed to be a psychology web site, but sometimes, you have a question you simply must know the answer to.
I frequently need to boil a mug of water, and I’ve often wondered what the most energy-efficient method is. Is it the microwave, or the good-old-fashioned teakettle on the cooktop? In these days of global warming, it’s an important question. So I finally decided to do the experiment.
Method and results:
I filled a ScienceBlogs mug with 300 ml tap water at 62° Fahrenheit.
Then I heated it at 30-second intervals in a 900-watt GE microwave oven.
Results are charted below:
I put an equal volume of water in a teakettle and heated over a 14,000 BTU gas burner until the kettle began to whistle. This took 189 seconds. The water was poured back into the mug and the temperature was found to be 190°
To heat water to an in-mug temperature of 190° it takes 150 seconds in a 900-watt microwave oven and 189 seconds using a teakettle on a 14,000-BTU burner.
The question, then, is how much energy is each device consuming for those time periods?
Let’s convert everything to kilowatt-hours.
2.5 minutes = .0417 hours
.0417 hours * 0.9 kw = 0.0375 kw-h
3.15 minutes = 0.0527 hours
0.0527 hours * 14,000 BTU/hr = 737 BTU = 0.216 kw-h
That means the stove consumed over five times as much energy as the microwave!
But how much electrical power is lost during transmission from the power plant to my house? According to Wikipedia, not much — about 7 percent. So the microwave oven is the clear winner for energy-efficient heating of a mug of water!
[fixed units 4/21 4:20 p.m. EDT]
[fixed equations 4/22 6:20 a.m. EDT]