Electric shower running cost: calculate yours

An electric shower running cost is not fixed by the label on the appliance. It depends on the shower's kilowatt rating, how long you run it, which power setting you choose and the electricity unit rate on your bill.

A 10.5 kW shower at full power for ten minutes uses up to 1.75 kWh. At 26.32p per kWh that is about 46p before any VAT on your bill. A shorter wash, an eco setting or a different tariff changes the figure at once. The daily standing charge is not part of one shower.

These are editorial calculations from published ratings and Ofgem's stated average for 1 October to 31 December 2026, which Ofgem says excludes VAT. We did not run a laboratory test. A qualifying purchase through our links can earn us a commission at no extra cost to you.

In short

Multiply the shower's power in kW by the time in hours, then multiply the result by your electricity price per kWh. Use the unit rate printed on your bill for the most relevant answer, and treat annual figures with caution unless they state the assumed shower length, frequency and power setting.

How to calculate your electric shower running cost

Find the energy first: power in kW times time in hours equals kWh. Then multiply kWh by your unit rate. Bills quote that rate in pence per kWh, so keep the sum in pence.

Ten minutes is 10 divided by 60 hours. A 10.5 kW unit at full rated power uses 10.5 times 10 divided by 60, which is 1.75 kWh. At 26.32p that is 46.06p, about 46p.

Use the unit rate on your bill, not the headline cap by default. Ofgem's published average for a Direct Debit customer on a default tariff from 1 October to 31 December 2026 is 26.32p per kWh, and Ofgem states that this figure excludes VAT. Region, tariff and payment method can still change what you pay.

Rated power is an upper limit, not a meter reading. A lower setting that switches to a smaller heating load makes the nameplate sum overstate consumption. A generic 9 kW assumption for a 10.5 kW shower understates it.

Worked examples for 8.5, 9.5 and 10.5 kW showers

The figures below use 26.32p per kWh, exclude VAT added to the bill, and assume full rated load throughout. Put your own bill rate in before you budget.

An 8.5 kW shower uses about 0.71 kWh in five minutes, 1.13 kWh in eight and 1.42 kWh in ten. At the example rate that is roughly 19p, 30p and 37p. Cutting ten minutes to eight saves about 7p under these assumptions.

A 9.5 kW shower uses about 0.79, 1.27 and 1.58 kWh over those same times, about 21p, 33p and 42p.

A 10.5 kW shower uses about 0.88, 1.4 and 1.75 kWh, about 23p, 37p and 46p. One hour at full load is 10.5 kWh and about £2.76, useful for checking the maths rather than for a normal wash.

The gap between 8.5 and 10.5 kW is about 9p over ten minutes at this rate. The higher rating may hold a stronger flow when the mains is cold. Running a weaker shower for longer can wipe out the saving.

Why eco, high and winter change the answer

An electric shower sets temperature by balancing heater output against flow. Triton's guidance describes high as more heat and eco as a lower-power position. Mira presents eco for a warm summer shower and high for colder winter conditions. Those settings change the input to the cost sum.

Eco does not cut consumption by a fixed half. The arrangement differs by model. If the manual states the load for each setting, use that number. A plug-in energy monitor is not suitable for a hard-wired high-power shower. Measurement needs the right equipment and a competent person.

Colder mains water needs a greater temperature rise. On high the shower may still draw its rated power, while you reduce flow to stay comfortable. In summer, eco may give enough heat at a usable flow. Why an electric shower goes lukewarm in winter sets out that trade-off. Two homes with the same 10.5 kW model can differ: one uses high for ten minutes in winter, another uses eco for six minutes in warmer months.

Daily, monthly and annual costs

Keep the assumptions attached to any yearly total. One ten-minute 10.5 kW shower at about 46p a day is roughly £13.82 over 30 days and £168.12 over 365 days, before VAT on the bill. Two showers a day double that energy. Five-minute sessions halve it. Holidays, eco use and the season make a flat 365-day multiply less realistic. A week of real times, multiplied by 52, is a better household estimate.

Leave the standing charge off each shower. Ofgem's stated average for the same October to December 2026 period is 54.83p per day, and you pay it whether the shower runs or not. It belongs in the whole-home budget.

Ofgem's cap applies in Great Britain, not Northern Ireland. In Northern Ireland, use your supplier's unit rate. In England, Scotland and Wales your tariff can still differ from the published average.

Electric shower versus combi boiler running cost

A 10.5 kW shower and a boiler's larger kW number are not the same comparison. The fuels differ, and a boiler's headline output is not the gas metered across your shower. Flow, temperature rise, efficiency and pipe losses all count. Electric shower or combi boiler shower covers the wider choice.

An electric shower heats cold mains at the point of use and needs no stored cylinder. All of its heat comes from electricity. A combi mixer blends boiler hot water with cold, so the cost follows the gas tariff and how the boiler performs.

Compare the same comfort: duration, litres if you can measure them, and the change on the relevant meter. A strong mixer can use more energy and water even when gas is cheaper per kWh. A restricted electric shower may use less water and feel weaker.

Purchase and installation sit outside running cost. The 11 kW electric shower comparison and the electric shower buying guide cover the product decision. A shelf price does not tell you efficiency.

How to reduce the cost

Time is the dependable saving when the power setting stays the same. Eight minutes instead of ten cuts calculated consumption by 20%. On the 10.5 kW example, 1.75 kWh falls to 1.4 kWh, about 9p at 26.32p per kWh before VAT.

Use eco when the temperature and flow are still comfortable, especially with warmer incoming water. A longer eco shower can cost as much as a shorter one on high. A timer is better evidence than a guess.

Leave a hard-wired shower assembled. If the temperature swings, or a protective device trips, stop using it and arrange a competent inspection. A lower unit rate cuts the shower line, but a higher standing charge can still raise the household bill.

What the running cost means when buying

At the example tariff, 8.5 kW instead of 10.5 kW moves a full-power ten-minute shower from about 46p to 37p. The lower rating has less heating power, so you may reduce flow more in winter for the same outlet temperature.

A higher-powered replacement is not automatically suitable for the existing cable, protective device or supply. Cable size and kilowatt rating are the limit, and a competent installer should assess them. Installation can cost more than the gap between two appliances.

A resistance heater turns electrical input into heat at the point of use, but controls, flow and session length still decide the bill. Use the kW-and-minutes formula, then take the unit rate from your current bill. Prices and settings change.