Thanks,
there is room for two emmersion heaters on my tank and I'm wondering if one will heat up the tank in 7 hours of off peak electricity from cold.
I have just replaced my hot water tank with a 210 litre one that is heated by indirect wood burner and a direct pumped oil fired condensing boiler. (ie it has two coils) My calculations show that its cheaper to heat the hot water overnight with off peak electricity (2p a unit!) and the tank has...