Energy waste that annoys me – Don’t fill up the kettle!

This post discusses a simple way to save energy, by only boiling the amount water you need to make your tea or coffee.


Making a tea… it’s a national institution, but how much energy does it take?

Today I did a quick calculation on the energy required to boil water, to check out just how significant it is. So here we are

My kettle takes 2 litres of water

The Specific Heat Capacity of water is 4.184j/g/k

Water from my tap is about 15C


So, 1 fill of the kettle takes

2 x 4.184 x 3600 x 1000 x 85 =  200Wh

To test this I used a electricity meter on the kettle, and found that I was in the right ball park, but the kettle seems to have losses of about 10%, so the actual consumption was 220Wh



220Wh is equivalent to leaving a 60W bulb switched on for 3 hours 40 minutes, but consumed in about 6 minutes.

So am I suggesting we stop drinking tea (or coffee)… no, I do love my coffee. Well lets consider this. My coffee mug can hold 250ml of coffee, slightly less if you allow for the milk. So why boil 2 litres of water if I need 1/8th that amount. Well exactly…

So next time you are making tea… just fill the kettle enough for the amount you are going to use. You could save more than 3 hours worth of lighting, along with it being faster… I like faster coffee.



BTW, isn’t funny that despite the fact that I’m a coffee drinker, I still talk about tea in this post constantly. It just seems to fit better… Comments on that are also welcome.


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3 Responses to Energy waste that annoys me – Don’t fill up the kettle!

  1. Yvette Kelly says:

    I am usually at home alone during the day and what I do is boil the kettle in the mornings and then fill up a flask for the rest of the day till the kids come home.And yes I drink a lot of coffee so my flask is big but keeps me going the whole day and the water remains hot.

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