Costs to heat water in different ways

davidlizard

Perhaps a silly question, but I cannot see if it has already been raised.

Supposing I want to make a cup of tea. What is the cheapest way to boil half a pint of water, assuming electric is at 9p/kWH and gas is at3p/kWH, and also roughly how much would it cost to heat the water in the following.

1. Electic kettle.
2. Kettle on a gas hob.
3. Microwave.

I guess as gas is cheaper per kWH, it should logically be the gas kettle, and it will be about 1/3 of the cost, but I would also guess the electric kettle is more efficient with the heat going into the water than around the sides?

Also, if I left a standard gas ring burning away for an hour, how many kWH is that likely to waste?

Whilst this may seem a bit frivolous when people have more serious concerns with energy prices, I would like to educate my wife/children about how expensive energy has become, and demontrate it in real world terms.

If I could remember my physics, I should be able to work this out for myself. I could measure the gas riing usage experimentally I guess, but all thoughts gratefully received.

Pound

Keep in mind it does take a lot longer to boil water on a gas hob.

looby-loo_2

I stand two saucepans in the sun with the lids on to take the chill is taken off the water so it boils quicker.