How much does a light bulb cost to run?
A typical light bulb costs about 1.1p per day to run. At 7 days a week that is 7.4p a week, or £3.83 a year, based on 8 W for 5 hours (0.04 kWh) at 26.32p per kWh.
Adjust for your light bulb
Worked example
8 W is 0.008 kW. Running for 5 hours uses 0.008 × 5 = 0.04 kWh. At 26.32p per kWh that costs 1.1p.
One LED bulb on for five hours a day costs £3.83 a year. An old 60 W filament bulb running the same time would use about seven times as much energy.
How to cut the cost
The big saving is replacing old filament or halogen bulbs with LEDs, which give the same light for a fraction of the power. After that, turn off lights in empty rooms, because five hours a day adds up across a house.
Questions
How much does it cost to leave a light on?
An 8 W LED costs 0.2p for each hour on, at 26.32p per kWh. Raise the power above to see a filament bulb.
Are LED bulbs worth the price?
Almost always. They cost a little more to buy but use roughly a seventh of the power of an old filament bulb and last much longer.
Other appliances
Electricity rate: Ofgem energy price cap, 1 October to 31 December 2026, Great Britain average, Direct Debit, default tariff: 26.32p per kWh. Your own tariff and region may differ, so change the rate above to match your bill. Appliance figures are typical estimates; your appliance's energy label or manual is more accurate. Last checked 2026-11-03. Next review: January 2027, when Ofgem announces the next quarter's cap.