LED Savings Calculator

How to use the LED savings calculator

Enter how many bulbs you are swapping, the wattage of the old bulbs and the new LEDs, how many hours a day they are on, and your electricity rate, and you get the dollars saved a year, plus the kilowatt-hours behind that number and the monthly figure. This is the whole-house version: it takes one bulb saving and multiplies it by how many you replace, so it answers what it costs you to leave incandescents in place across a kitchen, a hallway, or an entire house at once. The defaults describe the classic swap — ten 60 W bulbs for 9 W LEDs, four hours a day — which comes to 744.6 kWh and about $130.30 a year at the default rate.

Get the wattages right and the rest follows, but get the light output right first. A standard 60 W incandescent really does draw about 60 watts and puts out roughly 800 lumens, which is an efficacy of about 13 lumens per watt; the Energy Information Administration puts incandescent bulbs generally at 13 to 18 lumens per watt. A 9 W LED delivering the same 800 lumens is running at about 89 lumens per watt. That is the whole story of the swap in one comparison. Read the actual numbers off the bulbs rather than guessing, because a 60 W to 9 W swap saves substantially more than a 60 W to 12 W one, and if you are mixing bulb types, run the calculator once per group and add the results.

Be honest about hours, because runtime is the multiplier that decides whether a swap is worth doing at all. The lamp you read by for an hour at night is a very different bill from the porch light that burns from dusk to dawn or the kitchen ceiling that is on all evening. The default of 4 hours a day is a fair house-wide average, but a bulb that runs 10 hours saves more than twice what a 4-hour bulb does, and one that is on for a few minutes a day barely moves the needle. Start with the fittings that burn longest — porches, hallways, kitchens, stairwells — because those return the most for exactly the same effort and the same purchase.

The rate is the input that varies most, so use your own. The tool defaults to 17.5 cents per kWh; the Energy Information Administration reported a US residential average of 18.11 cents per kWh year to date for 2026 and 18.44 cents in May 2026, and state figures sit well above and below that. Add the per-kWh supply and delivery line items on your bill together, or divide a full month total by the kilowatt-hours used, and enter that figure — the dollar saving moves in step with it. Then read the result as an annual return on a one-time swap: the yearly figure repeats every year for the life of the bulbs, so the kWh number is the rate-free version and the monthly figure is the one to set against the rest of your power bill.

The formula

The saving is just the wattage you no longer draw, turned into energy and then into money. Each bulb watts dropped become kilowatts by dividing by 1,000, you multiply by the hours it runs and by the number of bulbs to get the energy saved a day, and you multiply that by the days in a year and by your rate to get the dollars. There is no efficiency term anywhere, because the calculation compares two devices doing the same job rather than converting between fuels.

What the arithmetic quietly assumes is that the new bulb produces the same light as the old one. That assumption is the whole basis of the comparison, and it is why lumens matter more here than watts do. Watts measure the power a bulb consumes; lumens measure the light it emits. With incandescents the two tracked each other closely enough that people learned brightness as a wattage, but LEDs broke that link, so the honest way to size a replacement is to match the lumen figure on the two boxes and let the wattage fall where it will.

daily kWh saved = bulbs × ((old watts − new watts) ÷ 1000) × hours per day
annual kWh saved = daily kWh saved × 365
annual saving = annual kWh saved × rate
efficacy in lumens per watt = lumens ÷ watts

Worked example with the defaults: 10 bulbs, each dropping from 60 W to 9 W, is 51 W saved per bulb, so 10 × 51 ÷ 1000 = 0.51 kW saved whenever the lights are on. Over 4 hours a day that is 2.04 kWh a day, which across 365 days is 744.6 kWh a year. At the default rate of $0.175 per kWh that comes to $130.30 a year, and the monthly figure the tool shows is 2.04 × 30 × $0.175 = $10.71. Push the runtime to 8 hours a day and every one of those figures doubles, which is why the fittings that burn longest are the ones to swap first.

Run the same two bulbs through the efficacy line and the comparison becomes plain. A 60 W incandescent putting out about 800 lumens is running at 800 ÷ 60 = 13.3 lumens per watt, which sits at the bottom of the 13 to 18 lumens per watt range the Energy Information Administration published for incandescent lamps. A 9 W LED delivering the same 800 lumens is at 800 ÷ 9 = 88.9 lumens per watt. That is close to seven times the light for each watt consumed, and it is the physical reason the saving is so large rather than a marketing claim.

The regulatory floor has moved under this comparison, which is worth knowing before you shop. The federal backstop standard requiring general service lamps to reach at least 45 lumens per watt took effect on 25 July 2022, with enforcement beginning in January 2023 for manufacture and import and in July 2023 for retail sale, and a 45 lumens per watt floor is already well above anything an incandescent or halogen lamp can reach. The Department of Energy then finalised a stronger standard on 12 April 2024 requiring more than 120 lumens per watt, with compliance from 25 July 2028. This calculator counts only the lighting saving, so in air-conditioned months the real total runs slightly higher, because heat an incandescent dumps into the room is heat your cooling has to remove again.

Frequently asked questions