LED Savings Calculator
Estimate annual electricity and cost change from replacing lamps with LEDs.
How the result changes
Only old lamp power changes; all other inputs stay at your current values. The line illustrates the formula across the shown range. This is not a forecast of real-world outcomes.
About this calculation
Comparing lamps by brightness label can hide the actual electricity change. This calculator uses input watts, number of lamps, operating schedule, and your electricity price to show annual energy and cost differences. Calculate LED savings when comparing household options.
Formula
annual kWh saved = (old watts − LED watts) × lamp count × hours/day × days/year ÷ 1,000
Worked example
With Old lamp power: 60 W, LED lamp power: 9 W, Lamps replaced: 8, Use per day: 4 h/day, Days per year: 365 days, Electricity price: 0.2 currency units/kWh, annual energy difference is 595.68 kWh.
Inputs and units
Read actual wattage from each old and replacement lamp. Enter the count of lamps switched, average operating hours per day, days of use per year, and price per kilowatt-hour from your tariff.
- Old lamp power (W): Use actual watts per old lamp, not an incandescent-equivalent label.
- LED lamp power (W): Use actual input watts per replacement LED lamp.
- Lamps replaced: Count lamps used on roughly the same schedule.
- Use per day (h/day): Estimate average daily operating hours.
- Days per year (days): Enter the number of days those lamps are normally used.
- Electricity price (currency units/kWh): Use your all-in or marginal rate consistently.
Calculation and worked example
Subtract new watts from old watts, multiply by lamp count and hours of use to get watt-hours, then divide by 1,000 for kilowatt-hours. Multiply the annual kilowatt-hours by the entered price for cost difference In compact notation, annual kWh saved = (old watts − LED watts) × lamp count × hours/day × days/year ÷ 1,000.
Replacing eight 60 W lamps with 9 W LEDs, used four hours daily for 365 days, changes demand by 408 W. Annual energy difference is 595.68 kWh; at 0.2 per kWh, estimated saving is 119.136 currency units.
How to use the answer
A positive result means the entered LEDs use less electricity. If new wattage exceeds old wattage, the negative figure means additional energy cost rather than a saving.
Compare LED options with different wattages, then consider brightness, colour temperature, and lamp life separately. For rooms with different use schedules, calculate each group on its own instead of using one average across all bulbs.
Assumptions and checks
Every counted lamp follows the entered schedule and electricity price stays fixed over the year. Fixture controls, dimming, heating interactions, purchase price, and replacement lifetime are not included.
A box saying '60 W equivalent' may describe brightness comparison while actual LED input could be around 9 W; using the equivalent number in the LED field erases the energy difference. Watts must also be converted to kilowatts before pricing.
At one lamp running one hour, kWh difference is watts difference divided by 1,000. At zero hours or equal lamp wattages, both annual differences must be zero.
Common questions
What does the annual energy difference result represent?
It is the yearly electricity difference for the entered lamp schedule, with positive values representing reduced kilowatt-hour use.
What should I check before relying on this result?
Confirm actual input watts, realistic operating hours, and the relevant electricity price; purchase and lifetime savings need a separate comparison.
Inputs
- Old lamp power (W)
- LED lamp power (W)
- Lamps replaced
- Use per day (h/day)
- Days per year (days)
- Electricity price (currency units/kWh)