Light Bulb Energy Cost Calculator
Calculate the cost of running light bulbs from wattage, number of bulbs, usage time and electricity tariff. Compare old bulbs with LED replacements, estimate yearly savings, payback time, kWh use and carbon emissions.
Calculator
Power rating per bulb.
How many bulbs with this wattage.
Average hours used daily.
Use 365 for everyday use.
Cost per kWh.
LED comparison
Compare your current bulbs against LED replacements.
Room/whole-home presets
Quickly estimate common lighting setups.
Advanced assumptions
Usually set to 0 for appliance-specific cost.
kg CO₂e per kWh.
Quick examples
Worked steps
Lighting comparison
| Setup | Wattage | kWh/year | Cost/year |
|---|
Common bulb running costs
| Bulb type | Typical watts | Daily cost | Yearly cost |
|---|
How the calculation works
The calculator converts bulb wattage into kilowatt-hours. Electricity suppliers charge per kilowatt-hour, usually shown as pence per kWh or cents per kWh.
For example, one 60W bulb used for 5 hours uses 0.3 kWh. At 28p/kWh, that costs about 8.4p per day before any standing charge allocation.
Ways to reduce lighting costs
Switch to LEDs
LED bulbs usually use much less electricity than incandescent or halogen bulbs for similar brightness.
Reduce unnecessary hours
Turning lights off in empty rooms cuts usage directly.
Use task lighting
A smaller lamp can be cheaper than lighting a whole room.
Use sensors or timers
Motion sensors can help with hallways, bathrooms, outdoor lighting and shared spaces.