How much does it cost to run a light bulb?
A light bulb with a typical power of 10 watts costs 0.3p an hour at the current price cap.
Uses Ofgem's price cap for 1 October to 31 December 2026: 26.32p per kWh, the average for Great Britain when paying by Direct Debit. Prices checked 13 November 2026.
Result
A light bulb (10 W) costs 0.3p an hour to run at the price cap rate of 26.32p per kWh.
an hour, to the nearest penny
| A day | 0.3p |
|---|---|
| A week | 1.8p |
| A month | 8p |
| A year | 96.1p |
| Electricity used in a year | 3.65 kWh |
That is under 1% of the 2,500 kWh a typical home uses in a year.
Show the workings
| Step | Sum | Answer |
|---|---|---|
| Turn watts into kilowatts | 10 W ÷ 1,000 | 0.01 kW |
| Cost of one hour | 0.01 kWh × 26.32p per kWh | 0.3p |
| Cost of one day's use | 0.3p × 1 hours | 0.3p |
| Cost of one week | 0.3p × 7 days | 1.8p |
| Cost of one year | 1.8p ÷ 7 × 365 days | 96.1p |
What this leaves out or assumes
- The standing charge is left out, because you pay it whether or not you use this appliance.
- A month is one twelfth of a year.
- The appliance draws its full power for the whole time it is on.
Where the figures come from
- Electricity unit rate, price cap, Great Britain average, Direct Debit: 26.32p per kWh. Source: Ofgem: Energy price cap unit rates and standing charges. Checked 13 November 2026.
- Typical yearly electricity use, medium user: 2,500 kWh a year. Source: Ofgem: Review of typical domestic consumption values, decision (Table 1). Checked 13 November 2026.
Typical power for a light bulb is from Centre for Sustainable Energy: How much electricity am I using?. Yours may differ: check its rating plate.
Cost by how long it runs
| Running for | Electricity used | Cost |
|---|---|---|
| 5 minutes | 0.001 kWh | under 0.1p |
| 10 minutes | 0.002 kWh | under 0.1p |
| 30 minutes | 0.005 kWh | 0.1p |
| 1 hour | 0.01 kWh | 0.3p |
| 2 hours | 0.02 kWh | 0.5p |
| 4 hours | 0.04 kWh | 1.1p |
| 8 hours | 0.08 kWh | 2.1p |
| 24 hours | 0.24 kWh | 6.3p |
Cost over a month and a year
If you used it this much every day:
| Used for | A month | A year |
|---|---|---|
| 30 minutes a day | 4p | 48p |
| 1 hour a day | 8p | 96.1p |
| 2 hours a day | 16p | £1.92 |
| 4 hours a day | 32p | £3.84 |
| 8 hours a day | 64p | £7.69 |
| All day, every day | £1.92 | £23.06 |
How much electricity does a light bulb use?
A light bulb rated at 10 watts uses 0.01 kWh of electricity for every hour it draws full power. Used for 1 hour every day, that is 4 kWh a year, under 1% of the 2,500 kWh a typical home uses.
Cost in your region
The price cap is different in each region. Running a light bulb for an hour costs 0.3p in East Midlands, the cheapest region, and 0.3p in Merseyside and Northern Wales, the dearest.
| Region | Price per kWh | Cost for an hour |
|---|---|---|
| East Midlands | 25.36p | 0.3p |
| Eastern England | 26.61p | 0.3p |
| London | 26.60p | 0.3p |
| Merseyside and Northern Wales | 27.86p | 0.3p |
| North Eastern England | 25.46p | 0.3p |
| North Western England | 26.49p | 0.3p |
| Northern Scotland | 26.35p | 0.3p |
| South Eastern England | 26.88p | 0.3p |
| South Western England | 26.58p | 0.3p |
| Southern England | 26.47p | 0.3p |
| Southern Scotland | 26.11p | 0.3p |
| Southern Wales | 26.55p | 0.3p |
| West Midlands | 25.60p | 0.3p |
| Yorkshire | 25.60p | 0.3p |
Paying by Direct Debit. Prices for other ways of paying.
How it compares
| Appliance | Typical power | An hour |
|---|---|---|
| Hairdryer | 2,000 W | 52.6p |
| Electric mower | 1,000 W | 26.3p |
| Light bulb | 10 W | 0.3p |
Running costs of every appliance
Checking your own light bulb
10 watts is a typical figure. Yours may be higher or lower. Look for the rating plate on the back or underside, find the number followed by W or kW, and put it in the calculator above.
Typical power is from Centre for Sustainable Energy: How much electricity am I using?, checked 13 November 2026. Prices are from Ofgem: Energy price cap unit rates and standing charges. The costs are our own sums.