[sclug] sclug Digest, Vol 116, Issue 11

John Stumbles sclug at yaph.org.uk
Wed May 22 18:12:43 UTC 2013

On 22/05/13 13:08, Neil Haughton wrote:

> All the heat from the immersion element goes into the water it is heating.
> A lot of  the latent heat in the gas goes up the flue or is lost from the
> boiler itself and the piping from boiler to water tank.
> The gap in price per kWh of useful heat is not as great as you might think.

The least efficient gas boilers out there (cast iron heat exchanger, 
permanent pilot light, natural draught flue) are about 65% efficient 
over a typical year's usage (SEDBUK rating). If yours has a permanent 
pilot and you switch it off for the summer[1] months you can effectively 
do a bit better (i.e. the boiler's at its least efficient in the summer 
when it's only doing HW, not CH) but I still doubt you'd get to break-even.

Also immersion heaters burn out a lot quicker when they're being used 
much of the time.

[1] FSVO 'summer' :-/

John Stumbles                                       http://yaph.org.uk

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