Electric boilers can be simple to install in some homes, but they use electricity for whole-home heat, so the monthly cost can climb quickly.
A 9kW electric boiler uses 9kWh in one hour at full output, costing about GBP 2.22 at 24.67p/kWh.
This page is a high-level cost sense-check, not an installer heat-loss design or tariff quote.
Current rate used: 24.67p/kWh electricity, 5.74p/kWh gas, based on Ofgem price cap, 1 April to 30 June 2026 for Direct Debit customers. Your actual tariff can differ by supplier, region, payment method and meter type.
The full-power column is the clean benchmark. The 65% column is a more realistic starting point for a thermostat-controlled heater in a warmed-up room.
| Heater size | Cost per hour | 2 hours | 7 days at 2h/day | 30 days at 2h/day | 30 days at 65% average output |
|---|---|---|---|---|---|
| 500W | £0.12 | £0.25 | £1.73 | £7.40 | £4.81 |
| 1kW | £0.25 | £0.49 | £3.45 | £14.80 | £9.62 |
| 1.5kW | £0.37 | £0.74 | £5.18 | £22.20 | £14.43 |
| 2kW | £0.49 | £0.99 | £6.91 | £29.60 | £19.24 |
| 2.5kW | £0.62 | £1.23 | £8.63 | £37.01 | £24.05 |
(watts / 1000) x hours x electricity price per kWh
For this page's 9kW example, 2 hours at full output costs £4.44. Used the same way for 30 days, it costs £133.22; at 65% average output it is closer to £86.59.
Short answers to the questions this page is built to solve.
It is using electricity for whole-home heat. Electricity unit prices are much higher than gas unit prices in the current Ofgem benchmark.
No. This page focuses on running-cost logic and should not replace quotes or a proper heat-loss assessment.