How do I work out what my own immersion heater costs?

Multiply the kWh it uses each time by your unit rate. At the Great Britain average of 26.32p a kWh, every kWh costs 26p.

Does it cost more in some parts of the country?

Slightly. The electricity unit rate under the cap runs from 25.36p a kWh in East Midlands to 27.86p in Merseyside and North Wales, so the same use costs about 10% more in the dearest region. Pick yours in the calculator.

Running costs

How much does it cost to run an immersion heater?

About £2.20 a full 150-litre cylinder from cold, at the price cap for 1 October 2026 to 31 December 2026. Used a typical household’s 95 litres of hot water a day, that’s about £425 a year.

Heating a 150-litre cylinder from 12°C to 60°C takes about 8.37 kWh. A typical household uses about 95 litres of hot water a day, about 4.4 kWh of heat, by the government’s SAP method; the cylinder’s own heat losses add more, especially if it’s old or poorly insulated.

Verified: 23 October 2026 from Ofgem price cap rates

Work out yours

Your electricity price

Energy for one full 150-litre cylinder from cold

kWh

Times a week

A full 150-litre cylinder from cold

£2.20

A week

£8.15

A month

£35.42

A year

£425

1,615 kWh a year. Unit rate only: the standing charge is paid whether or not anything is switched on.

An immersion heater is a 3 kW element in your hot water cylinder, so it costs the same per hour as a 3 kW heater. How long it runs depends on how much hot water you use and how well the cylinder holds its heat.

On a single-rate tariff it is an expensive way to heat water if you also have gas. On Economy 7, with the immersion on a timer for the cheap night hours, it costs much less.

Ways to spend less

Put it on a timer rather than leaving it on all the time.
Fit a cylinder jacket if your cylinder doesn’t have factory foam insulation.
If you have Economy 7, heat the water overnight.

Compared with

Appliance	Typical cost	A year, used as shown
Immersion heater	£2.20 a full 150-litre cylinder from cold	£425 (a typical household’s 95 litres of hot water a day)
Electric shower	30p an 8-minute shower	£109 (one 8-minute shower a day)
Kettle	4p a boil	£66 (five boils a day)

At the Great Britain average electricity rate of 26.32p a kWh.

Common questions

How much does it cost to run an immersion heater?: About £2.20 a full 150-litre cylinder from cold, at the price cap for 1 October 2026 to 31 December 2026. Used a typical household’s 95 litres of hot water a day, that’s about £425 a year. Heating a 150-litre cylinder from 12°C to 60°C takes about 8.37 kWh. A typical household uses about 95 litres of hot water a day, about 4.4 kWh of heat, by the government’s SAP method; the cylinder’s own heat losses add more, especially if it’s old or poorly insulated.
How do I work out what my own immersion heater costs?: Multiply the kWh it uses each time by your unit rate. At the Great Britain average of 26.32p a kWh, every kWh costs 26p.
Does it cost more in some parts of the country?: Slightly. The electricity unit rate under the cap runs from 25.36p a kWh in East Midlands to 27.86p in Merseyside and North Wales, so the same use costs about 10% more in the dearest region. Pick yours in the calculator.

Other appliances

Add up several appliances in the electricity cost calculator, or see what your own home uses with the smart meter analyser.