. . . back to part 5 . . .

How much is inside hot water? - part 6

The final installment of the hot water saga

How does the microwave compare with the kettle and the pan?

A quick recap: the kettle method used 0.11 kWh of electrical energy to boil the kettle
0.06 kWh of chemical energy to bring the water to the boil in the pan;
the pan (with lid) method used about 0.3 kWh of chemical energy.


I put one litre of water in my "900 W" microwave and set it going on high power for 7mins 30secs, which was the time I reckoned it should take to deliver 0.11 kWh (which is what the kettle had needed to deliver).

I peered through the window and saw no evidence of boiling. I gave it another 1 minute.

I peered through the window and saw no evidence of boiling. I gave it another 2 minutes. I started to wonder whether the microwave's fan was actually cooling down the water and it was never going to boil.

I gave it another 1 minute.

At this point I took out the bowl and removed the lid, and found that a few bubbles were forming. When I banged the bowl on the counter, more bubbles appeared and fizzed at the surface. I decided to call this "boiling".

That was 11minutes 30 seconds - nearly four times as long as the plastic kettle. The electrical energy used, measured at the socket, was 0.25 kWh. (The microwave must have been sucking about 1.3 kW, by the way.)

To finish off, as with the kettle, I put the water in a pan, and brought it to the boil using gas in 70 seconds, using 0.215 cubic feet (0.07 kWh)

In conclusion, the microwave is by far the worst method of heating water for making pasta.

  1. It takes longer than all other methods.
  2. It uses more energy in the home (0.32 kWh) than all other methods.
  3. It uses more energy in toto (0.25 x 2.7 + 0.07 = 0.74 kWh) than all other methods.
  4. You can't tell what is going on inside the pot inside the microwave.

Down with microwaves!

Before the Microwave Promotion Association gets onto me, I take back my intemperate outburst straight away. I love my microwaves. There is no better way to make a mug of hot milk than a 1 minute 20 second zap!

Dasher - efficient communication with any muscle

Tapir - a simple 12-key disambiguating keyboard.


This page is a tribute to cockeyed.com

To find out more energy numbers, you might like to read my book Sustainable Energy - Without the Hot Air.

David MacKay
Last modified: Tue Jun 24 00:56:10 2008