Domestic water heating

the_bard_2

I have a new oil-fired central heating system for heating and hot water. When the CH is off, is it cheaper to use the boiler just for hot water, or an electric immersion heater? The immersion has two elements, the smaller heats just the top third of the cylinder whilst the oil boiler heats the whole tank. I need enough for 1 shower and 1 lot of washing up per day.

Cardew

Welcome to the forum.

There have been threads on this subject.

A litre of oil produces 10.2 kWh. Assuming your new boiler is 90% efficient that means at, say, 65p a litre it costs approx 7p for a kWh.

Your electricity cost, ??? - 10p for a kWh.

So if the small immersion produces enough HW that will probably be a little cheaper.

However a well lagged tank even if full of HW will lose surprisingly little heat over a 24 hour period - about 2-3 kWh.

Overall there probably is not much in it either way.

samtheman1k

Cardew wrote: »

Welcome to the forum.

There have been threads on this subject.

A litre of oil produces 10.2 kWh. Assuming your new boiler is 90% efficient that means at, say, 65p a litre it costs approx 7p for a kWh.

Your electricity cost, ??? - 10p for a kWh.

So if the small immersion produces enough HW that will probably be a little cheaper.

However a well lagged tank even if full of HW will lose surprisingly little heat over a 24 hour period - about 2-3 kWh.

Overall there probably is not much in it either way.

Those figures are quite shocking actually. Npower are doing an electricity tariff for around 7.5pkwH (after 728 units at a higher rate, 22p IIRC). It seems as if the time for direct electric heaters will become cheaper than oil fired heating isn't far away!!! (and has probably already passed for those of you with older more inefficient boilers!)