Random math question about electricity usage!

[Bayleaf]

Mr Bayleaf likes to heat his coffee cup in the microwave before filling it with coffee from the machine. 1 1/2 minutes on full power, in a 900watt mw. I've been making his coffee this week, as he's hobbling around with a foot problem, so I've been boiling the kettle with a cupful of water in it, and using that to heat the cup (which I think heats the cup better anyway ...)

Which method is the more efficient/cheaper?

I say kettle, he says microwave!

(If the woodburner was already going, with a pre-warmed kettle on it, we'd use that - but we don't light the woodburner first thing yet).

Your math question for the day!

[niemeyjt]

How many Kw is the kettle?

How long does it take to boil the water?

edit - just reread - it is an empty cup in the microwave - microwaves work on the O-H bond in water - they heat water - not dry china - unless he first wets the cup.

[Bayleaf]

Kettle is probably 1200w. To boil one cupful of water, takes less than a minute (will time it next time!). It's a dry cup that is put in the microwave.

If I can then re-use the hot water for something else, that's a bonus!

[niemeyjt]

Try wetting outside of cup and giving it 30 seconds in microwave - as I say a microwave works on water.

[MAD87]

You'll wreck the microwave if the cup is dry.

[Bayleaf]

You'll wreck the microwave if the cup is dry.

Ah! Interesting point! Thank you!

[exile]

And if the cup does heat up, it indicates that the cup itself is not microwave safe.

[hughnique]

Does the coffee machine not deliver hot coffee then??

[Hotrodder]

We make a batch of coffee in the machine and let it sit with power off. When I want a cup I pour from the jug into a cup and microwave that to heat it. I wouldn't dream of farting about heating the cup separately.

[Bayleaf]

Does the coffee machine not deliver hot coffee then??

It's an espresso machine, so not, not scorching hot - especially for making a mug of coffee.