Emersion heater V gas boiler

Worried_of_wakefield

Any clever engineers out there?
I have  for a further 5 months off peak electricity charges at 5p/kWh, I can relatively easily bring the HW cylinders 3kW emersion heaters on line.
Presently I heat my water via a gas boiler at 5.8p/kWh for a further 12mth, I would add the boiler is 20+ yr old so unsure how efficient it is.
Q- Whilst a simple comparison of 'present' rates appear to suggest probably stick with gas, can anyone tell me if heating water is generally more efficient either way

QrizB

There might not be a lot in it.

Assuming that your HW tank takes 10kWh to heat:

• Electric: 100% efficient, 50p + 10p (see below).
• Gas: if 80% efficient, 72p.

If you're heating the water electrically during the wee small hours but not using it until the following evening, you'll lose some heat from the tank. If you lose 2kWh that's an additional 10p to add to the electrical cost. (You won't get this loss with gas if you heat the water shortly before using it).

Of course, if your gas boiler is really ancient it won't be 80% efficient.

• Gas: if 60% efficient, 97p.

In this case electric is the clear winner.

xeny

Over the winter, you might appreciate the waste heat from the hot water cylinder leaking into the house, which would make the decision easier.