Light Bulb Cost Calculator

About this calculator

The running cost of a light bulb is calculated by converting its power draw from watts to kilowatts, multiplying by the daily hours of use to get daily energy consumption in kilowatt-hours (kWh), then multiplying by your electricity rate per kWh — the annual cost simply extends the daily figure across 365 days, and multiplying by the number of bulbs scales the total for a whole fixture or room.

Homeowners run this calculation when deciding whether to switch from incandescent or halogen bulbs to LEDs, because the wattage difference is dramatic — an LED producing the same brightness as a 60W incandescent typically draws only 8-10W — so even though LED bulbs cost more upfront, the ongoing electricity savings recoup that premium within months for bulbs used several hours a day, and the calculation is also the standard way to estimate the impact of leaving lights on unnecessarily.

This calculator takes the bulb wattage, daily hours of use, your electricity rate and the number of bulbs and returns both the monthly and yearly running cost.