My 1965 'Basic Tables in Electrical Engineering' gives the Heat of Vaporization 
of Water as 972 Btu/Lb   so there is quite a bit of conversion required!

On 29/08/2022 12:28, Peter Merchant via dorset wrote:
I had considered that, but it's so long ago in my ancient past that I studied 
thermodynamics, I didn't look into calculating it. My concern about it is the 
cost of raising the temperature to 100 deg, then the latent heat of 
vaporisation to actually boil it.

Peter M.   [ Applies to any form of boiling water of course. ]

n 29/08/2022 11:31, Ian Morris via dorset wrote:
500ml of water = 500g water.  let's assume you want to go from 20-100 C => 
increase of 80C
Specific heat capacity of water = 4.184 J/g-K
=> 167,360 J = 0.0465 kWh Electricity @27p/kWh = 1.2552p

So rather similar???? (OK, I don't know efficiency of electric kettle ... but 
heating elements are 100% efficient... sure there will be some losses to both 
the kettle and the wider environment, but i doubt somehow that they are 
huge....) Of course this is about cost for the consumer ... I'm totally 
ignoring the ineffeciency of turning gas into electricity and transmitting it 
around the country in the first place.

On 29/08/2022 09:33, Peter Merchant wrote:
I was curious, so I took the water from the kettle and put it in a pot on the 
stove. It was very close to 500ml.

Watching the gas meter while it boiled it used 0.014 m(cubed) of gas, which 
converted to 0.15788Kwh and at my current rate of 7.123p/Kwh cost me 1.1.25p to 
boil up.

Unfortunately I can't see my electricity meter easily to see what it costs me 
to boil that amount in the kettle or by Microwave. Does anybody have that 
facility?  And also there is always other electricity being used.



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