Operating cost
LED Savings Calculator
Enter the existing wattage, the replacement wattage, hours per day, and your bill rate. The page prices the yearly energy difference. It is not a second appliance scheduler.
Numbers stay in this browser. EnergyToolMage does not upload your inputs or require an account.
Formula
kWh/year = W × hours/day × 365.25 ÷ 1000; saved kWh = old − new; saved $ = saved kWh × USD/kWh
Assumptions
- Both lamps run the same hours per day, every day of a 365.25-day year.
- Watts are constant while on.
- Example rate $0.16/kWh is illustrative only.
How it works
Each wattage uses watts × hours/day × 365.25 ÷ 1000. The dollar result is that energy times your rate. The primary number is the yearly difference.
Inputs and results
Inputs: old W, new W, hours/day, USD/kWh. Outputs: yearly kWh and USD for each lamp and the delta.
Worked examples
60 W vs 9 W, 3 hours/day, $0.16/kWh
Yearly energy 65.745 kWh vs 9.862 kWh. Difference 55.883 kWh and $8.94 at the example rate.
How to use this calculator
- Enter the existing wattage and the replacement wattage.
- Enter hours of use per day (cannot exceed 24).
- Enter your electricity rate in USD/kWh.
- Read yearly kWh and dollars for each lamp and the difference.
Limitations
- Does not include bulb purchase price or payback years.
- Does not certify ENERGY STAR, lumens, or color quality.
- Does not model dimming or occupancy sensors unless you change hours.
Sources and freshness
- Every rate, wattage, hour, and loss percentage is a user input or a labeled example. Nothing here is a live utility tariff.
- The $0.16/kWh figure that appears in examples is an illustrative default, not a U.S. average and not current.
- Annualization uses 365.25 days per year and 365.25 ÷ 12 days per month. Your billing cycle will differ.
Questions
Why not use the appliance calculator twice?
You can. This page exists for the named LED/CFL-vs-LED job: two wattages, one schedule, one delta.
What if the new bulb uses more watts?
The difference can be negative. The math does not force a savings story.
Is there a default hours-per-day from a lighting study?
No. Hours are a user input. No unverified lighting-hours benchmark is shipped.
Related energy tools
- Appliance costUse this when you know an appliance’s watts and how often you run it. The page annualizes with a disclosed calendar convention and your bill rate.
- Electricity costMultiply energy you already know in kilowatt-hours by the dollars-per-kWh on your bill. Use this when a meter, EnergyGuide label, or another calculator already gave you kWh.
- kWh from wattsKilowatt-hours are power times time. Enter watts or kilowatts and how long the load runs. Optionally price the energy with your own rate.