What's the cheapest way to heat my water during the summer? I've a regular oil fired boiler system that heats water in a hot water cylinder and also does the central heating when required.
My oil is about 38p/l, electricity roughly 5p/kWh plus a standing charge but that's kinda irrelevant since I'll pay that either way.
I've read lots of heated (sorry) discussions about efficiency of heating the water tank with the oil burner vs. the electrical immersion heater. I'm happy to assume that electrical is more efficient than oil method but not by a massive amount. Obviously the oil method has to heat the pipes, loses some energy out the flue and needs electricity itself to drive the pump.
I guess the question is roughly how much energy does an average oil boiler get from a litre of oil?
The interweb figures I've found suggest 11.5kWh from a litre of oil, or 3.3p/kWh.
So oil energy is roughly 2/3 the cost of electricity energy.
So my oil boiler would have to be better than 66% efficient at converting the energy from the oil into energy directly heating the water?
It sounds like oil method should be better, anyone feel like wading in?!