How much does a 3kW heater cost to run?
What a 3kW electric heater costs per hour, per day and per month at the Ofgem price cap, and how to make it cheaper.
3kW heater: running cost per hour, day, week and month
| Use | Per day | Per week | Per month | Month on thermostat* |
|---|---|---|---|---|
| 1 hour a day | 79.0p | £5.53 | £23.69 | £14.21 |
| 2 hours a day | £1.58 | £11.05 | £47.38 | £28.43 |
| 3 hours a day | £2.37 | £16.58 | £71.06 | £42.64 |
| 5 hours a day | £3.95 | £27.64 | £118.44 | £71.06 |
| 8 hours a day | £6.32 | £44.22 | £189.50 | £113.70 |
At the Ofgem price cap (26.32p/kWh, Direct Debit, national average). * A heater on a thermostat heats about 60 % of the time once the room is warm. Your standing charge (54.83p/day) is paid whether or not you use the heater.
How to work it out yourself
Watts ÷ 1,000 × hours × your unit rate. A 3kW heater for 3 hours: 3.0 × 3 = 9.0 kWh, × 26.32p = £2.37. Your unit rate is on your bill; on Economy 7 it depends on the time of day (see storage heaters and Economy 7).
Every heater, side by side
| Power | 1 hour | 3 hours a day, a month | On a thermostat* |
|---|---|---|---|
| 500 W | 13.2p | £11.84 | £7.11 |
| 1 kW | 26.3p | £23.69 | £14.21 |
| 1.5 kW | 39.5p | £35.53 | £21.32 |
| 2 kW | 52.6p | £47.38 | £28.43 |
| 2.5 kW | 65.8p | £59.22 | £35.53 |
| 3 kW | 79.0p | £71.06 | £42.64 |
At the Ofgem price cap (26.32p/kWh, Direct Debit, 1 October to 31 December 2026). * A heater on a thermostat is assumed to heat about 60 % of the time once the room is warm.
3kW heaters we recommend
Dimplex DXFF30TSN 3kW Fan Heater
- Fan heater · 3,000 W
- A 3 kW flat fan heater from Dimplex with two heat settings, a thermostat with frost setting and a cool-blow option: lots of heat fast for a garage, workshop or large cold room.
- Costs 79.0p an hour at full power.
Dimplex RUG3TS Rugged Workshop 3kW Fan Heater
- Fan heater · 3,000 W
- Steel-cased 3 kW workshop heater (1.5 or 3 kW) with thermostat and frost setting, tilt switch, dust filter and IP21 drip protection: built for garages and workshops, not living rooms.
- Costs 79.0p an hour at full power.
Dimplex ML3TSTIE7 3kW Convector Heater
- Convector heater · 3,000 W
- The 3 kW version: electronic thermostat accurate to about 1 °C, frost protection and a 7-day timer with four schedules a day, for large or poorly insulated rooms.
- Costs 79.0p an hour at full power.
If you buy through our links, Amazon pays us a small commission. The price is the same for you.
Frequently asked questions
How much does a 3kW heater cost per hour?
79.0p at full power at the Ofgem price cap (26.32p/kWh).
How much does it cost to run a 3kW heater all day?
Eight hours at full power is about £6.32; on a thermostat, closer to £3.79.
Are some electric heaters more efficient than others?
No: every electric heater turns 1 kWh of electricity into 1 kWh of heat. Running costs depend on the power, how long it is on and its controls (thermostat, timer).
Running costs use the Ofgem energy price cap, 1 October to 31 December 2026: average unit rate for electricity paid by Direct Debit (26.32p/kWh, standing charge 54.83p/day) and gas (7.97p/kWh). National averages; your region and tariff may differ. Prices on Amazon change: check the live price before you buy.