Quick answer: a storage heater costs its rating × charging hours × your night electricity rate. A typical 2.55kW heater charging for 7 hours uses 17.85 kWh: about £2.50 a night at a 14p night rate, or £4.70 if the same energy were bought at the 26.32p day-rate cap.
Storage Heater Running Cost Calculator
Results update as you type. Enter your Economy 7 or off-peak night rate below.
How storage heater running cost is worked out
Cost per night = rating in kW × charging hours × input setting × night rate
A 2.55kW heater on a full charge for 7 hours: 2.55 × 7 = 17.85 kWh. At 14p per kWh that is £2.50. If the input dial is at about 60%, it stores roughly 60% as much and costs about £1.50. Day-rate figures use 26.32p per kWh, the Ofgem price cap unit rate for electricity paid by direct debit from 1 October to 31 December 2026. Your own rate is on your bill, so change it in the calculator.
Storage heater costs by size
| Rating | Energy per 7-hour charge | At a 14p night rate | At 26.32p (day-rate cap) | Winter at 14p (26 weeks) |
|---|---|---|---|---|
| 1.7kW | 11.9 kWh | £1.67 | £3.13 | £303.21 |
| 2.55kW | 17.85 kWh | £2.50 | £4.70 | £454.82 |
| 3.4kW | 23.8 kWh | £3.33 | £6.26 | £606.42 |
The 14p column is an example rate to show the method, not a price you will necessarily pay. The comparison with the day-rate cap shows why storage heaters only make sense on a tariff with cheaper night electricity.
Input and output dials explained
- Input (charge): sets how much heat is stored overnight, so it controls the cost. Turn it down on milder nights.
- Output (boost): sets how quickly the stored heat is released. Keep it low in the morning so heat lasts into the evening, then turn it up when you need it.
- Convector or boost heater: if your model has one, it runs on daytime electricity. Check the rating and cost it separately with our electric heater calculator.
Worked examples
- Mild week: a 1.7kW heater on a 60% input setting for 7 hours stores about 7.1 kWh, roughly £1.00 a night at 14p.
- Cold snap: three 3.4kW heaters on full charge use 71.4 kWh a night between them, about £10.00 at 14p.
Frequently asked questions
How much does a storage heater cost to run per night?
Multiply its rating by the hours it charges and your night rate. A 2.55kW heater charging for 7 hours uses 17.85 kWh. At an example night rate of 14p that is about £2.50 a night; at the 26.32p day-rate cap it would be about £4.70.
Do storage heaters only use cheap night electricity?
The main element charges overnight on an Economy 7 or similar tariff. Many models also have a boost or convector heater that runs on the day rate, which costs far more, so use it sparingly.
How do I lower storage heater costs?
Turn the input (charge) dial down in milder weather so it stores less heat, keep the output dial low until you need heat, and keep doors closed in heated rooms.
Is a storage heater cheaper than an electric heater?
Per kWh it can be, because it charges at the night rate. If your night rate is half your day rate, the same heat costs half as much. The trade-off is that the heat is released through the day whether or not you are in.
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