What does this tool do?
LEDs use a fraction of the power of incandescent bulbs for the same light output. This calculator multiplies the wattage difference by the hours the lights are on and applies your electricity rate to estimate the annual saving.
The Formula
kWh saved = bulbs × hours per day × 365 × (old watts − new watts) ÷ 1000; saving = kWh × rateFrequently Asked Questions
Do LEDs really last longer?
Yes, quality LED bulbs are typically rated for 15,000 to 25,000 hours, compared with about 1,000 for incandescent. Longer life adds to the saving beyond electricity.
Why is the saving smaller in winter?
Old incandescent bulbs release heat, so they add a little warmth in winter. In heated homes the net saving is slightly below the simple electricity calculation.