LED Lighting Savings Calculator
Enter how many fixtures you have, what they draw now and what the LED replacements draw, how long they run and your electric rate. You get the annual energy cost before and after, the savings in kWh and dollars, and the simple payback on the LED cost. Works for a house, a shop or a whole building.
Your numbers
Result
Enter your numbers to see the result.
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The math
- Annual kWh = fixtures × watts × hours per day × days per year ÷ 1,000, figured once for the existing lights and once for the LEDs.
- Annual cost = kWh × your rate. Savings = the difference.
- Simple payback = total LED cost ÷ monthly savings. It ignores interest, rebates and the lamps you no longer buy, so the real payback is usually shorter.
When choosing the LED, match the light output in lumens, not the watts. A 60 W incandescent gives about 800 lumens, which a 9 W LED matches; a 4-lamp T8 troffer gives about 10,000 lumens, which a 35 to 40 W LED panel matches.
Worked example
Twenty 60 W lamps on 8 hours a day, 365 days a year, at 17 ¢ per kWh use 3,504 kWh and cost $596 a year. Nine-watt LEDs use 526 kWh and cost $89. The retrofit saves 2,978 kWh and $506 a year, and at $5 per lamp ($100 total) it pays for itself in 2.4 months.
Frequently asked questions
What electric rate should I use?
Divide the total of a recent bill by the kWh used, so delivery charges, riders and taxes are included. Residential rates in the U.S. are mostly 12 to 30 ¢ per kWh; commercial rates can be lower per kWh but add demand charges.
Does it include the ballast?
Only if you include it in the watts. Fluorescent and HID fixtures draw more than the lamp rating because of the ballast, so use the fixture input watts from the ballast label.
Why is the payback shorter in practice?
LEDs last 25,000 to 50,000 hours, so you also stop buying and changing lamps, and many utilities offer rebates on LED retrofits. Those savings are not in this estimate.
Does lighting affect heating and cooling costs?
Yes. Old lamps give off heat, which helps a little in winter and hurts in summer. The effect is small for most spaces and is not included here.
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This calculator gives an estimate for planning and is not tax, legal or engineering advice. Confirm code-related results against the code edition adopted in your jurisdiction and with your authority having jurisdiction, and follow the manufacturer's instructions.