- A storage heater's cost is its input power x the hours it charges x your off-peak unit rate. For example, a 2.22 kW input charging for 7 hours uses 15.54 kWh: put your own off-peak rate in the calculator. At the single-rate cap average of 26.32p it would be £4.09, but most storage heaters charge on a cheaper off-peak rate.
- Prices from the Ofgem price cap, 1 October to 31 December 2026: the average for England, Scotland and Wales is 26.32p per kWh by Direct Debit. Your region and tariff change it, so use the calculator below.1
- Last checked: 28 October 2026.
Worried about bills this winter? See the help and savings you may be missing, free. Check my bills
Storage heater charging cost at the single-rate price
For comparison only: these use the single-rate average of 26.32p per kWh. On an Economy 7 or other multi-rate tariff, your off-peak rate is lower, so use the rate on your bill in the calculator.
| Power | 1 hour | 3 hours | 7 hours |
|---|---|---|---|
| 1.02 kW | 26.8p | 80.5p | £1.88 |
| 2.22 kW | 58.4p | £1.75 | £4.09 |
| 3.3 kW | 86.9p | £2.61 | £6.08 |
How to work out the cost
Multiply the power in kilowatts by the hours it runs, then by your electricity unit rate. If the power is in watts, divide by 1,000 first.
For example: 2.22 kW x 7 hours x 26.32p per kWh = £4.09.1
That is the cost at full rated power. If a thermostat switches the appliance off once the room is warm, it uses less. Standing charges are paid whatever you use, so they are not part of the cost of switching it on.
Use your own off-peak rate
Ofgem does not publish one Economy 7 night price. It says: “For multi-rate tariffs like Economy 7 you will pay one unit rate during peak hours and a different unit rate during off-peak”, and “Together, they cannot be more than the price cap.”1
So check your off-peak (night) unit rate on your bill or app, and type it into the calculator as your rate. The calculator's regional rates are for single-rate tariffs.
Typical storage heater input power
Dimplex describes its Quantum storage heater as one that “stores up low-cost, off-peak energy to be used on demand through the day”. Its catalogue lists charge input ratings of 1,020 W, 1,560 W, 2,220 W, 2,760 W and 3,300 W across the range (tolerance +5%/-10%).2 Models are named only as examples of published ratings, not recommendations.
The input rating is what you pay for while it charges. The output rating (for example 1 kW) is the heat it gives out, so a “1 kW” heater can take 2.22 kW while charging.
Next steps
1. Find the input rating (in W or kW) on your storage heater's label.
2. Find your off-peak unit rate and the hours of your off-peak period on your bill.
3. Input x hours x off-peak rate gives the cost of one full charge.
Help with energy bills
If you are struggling with energy bills, check the help you may be able to get. These checkers are free and need no account.
Who these figures cover
The prices are from Ofgem's price cap for England, Scotland and Wales, 1 October to 31 December 2026.1 In Northern Ireland, use the unit rate on your bill in the calculator.
There is no VAT on household electricity in England, Scotland and Wales, and the rates above already reflect this.1 HMRC: “The temporary zero rate applies from 1 October 2026 to 30 June 2027.” The Budget on 28 October 2026 extended it from 31 March (announced; the legislation is due in early 2027). Gas stays at 5% VAT.4