Light Bulb Running Cost Calculator UK
Work out exact costs for your bulbs based on usage and current tariffs.
Typical Yearly Costs (4.5 hrs/day, 26p/kWh, 1 bulb)
| Bulb Type | Wattage | Yearly Cost | Lifespan (hrs) |
|---|---|---|---|
| LED | 8-15W | £3-£6 | 50,000 |
| CFL | 10-20W | £5-£10 | 8,000-10,000 |
| Halogen | 40-70W | £20-£40 | 2,000 |
| Incandescent | 40-100W | £15-£45 | 1,000 |
How Costs Work
Costs arise from power (watts) converted to energy (kWh) over time. Formula: (watts / 1000) × hours × tariff / 100. Multiplied by days in period and bulb count. Equivalents match light output: 10W LED ≈ 40-60W incandescent.
Frequent Questions
UK bills charge per kilowatt-hour; check your latest statement for the exact rate, often varying by time of day.
Dimming cuts power proportionally, lowering costs, but select dimmable bulbs to avoid flicker or reduced life.
Longer life like LEDs (50,000 hrs) reduces replacements; total cost includes bulb price over years of use.
They add minor standby draw (0.5W); factor into average wattage for accuracy.
Common Mistakes
- Overlooking multiple bulbs or rooms, multiplying small savings into large totals.
- Ignoring peak/off-peak tariffs; average them for realistic figures.
- Comparing watts directly; match lumens (light output) instead for true equivalents.
- Forgetting bulb life; cheap incandescents need frequent changes, hiking real expenses.
References
Ofgem. (2025). Electricity price cap factsheet. Retrieved from https://www.ofgem.gov.uk/information-consumers/energy-advice-households/energy-price-cap
Department for Energy Security & Net Zero. (2024). Energy efficiency in lighting: Technical guidance. Retrieved from https://www.gov.uk/government/publications/energy-efficiency-lighting
Energy Saving Trust. (2025). Home lighting costs and savings report. Retrieved from https://energysavingtrust.org.uk/advice/lighting/