hot water house energy efficiency

So the microwave oven is the clear winner for energy-efficient heating of a mug of water! [via cognitive daily]

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.

The microwave: 2.5 minutes = .0417 hours * 0.9 kw = 0.0375 kw-h
The stove: 3.15 minutes = 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.