LED Savings Calculator

How the calculator turns watts into dollars

Every bulb in the house is a small meter running. A 60 watt bulb that burns for 1,000 hours pulls 60 kilowatt hours off the grid, and a 9 watt LED in the same socket pulls 9. The saving is the gap between those two numbers, multiplied by the hours the light is on and by what your utility charges for a kilowatt hour.

The arithmetic in the box above is: bulbs × (old watts − new watts) × hours per day × 365 ÷ 1,000 = kilowatt hours saved in a year. Multiply by your rate and you have dollars. Divide the price you paid for the bulbs by the yearly saving and you get payback, the number most people want, because it says how long the bulbs have to survive before the swap has paid for itself.

Two inputs move the answer more than the rest: hours of use and your electric rate. A bulb in a closet that runs 20 minutes a day is not worth a trip to the store. The same bulb over a kitchen counter at 6 hours a day is worth replacing even at a premium bulb price. The calculator is built so you can test both cases in a few seconds.

What to enter, and where to find each number

Old bulb watts. The wattage is stamped on the glass or on the metal base, and on older bulbs it is often the only marking. If it has rubbed off, a standard A19 shape in a living room is usually 60 watts, a globe over a bathroom mirror is usually 40 to 60, and a floodlight in a recessed can is 65 to 75.

New LED watts. The box always lists it, and for a bulb that matches a 60 watt incandescent it is usually 8 to 10 watts. Watch for the word equivalent: a package that says 60W replacement is describing light output, not power draw, and the real figure is the small number next to it.

Hours per day. A rough count beats a precise guess. Kitchen and family room lights commonly run 4 to 6 hours, bedrooms 1 to 2, a home office 6 to 8, and a porch on a timer 5 to 8. If a room has two bulbs on one switch, count the hours once and enter the bulb count.

Electric rate. Take the total on your bill, divide by the kilowatt hours listed, and you have your all in rate, which is higher than the supply rate because it carries delivery charges. The EIA monthly price table puts the 2025 US average residential price at 17.3 cents per kilowatt hour, with state averages running from about 11.8 cents in North Dakota to 40.6 cents in Hawaii. The default of 17 cents in the calculator is that national average, rounded.

Price per bulb. A standard 9 watt A19 has been around $3 for a while. Recessed retrofit kits, candelabra shapes and smart bulbs cost more, and a bulk pack usually lands under $2 per bulb.

Example: ten living room bulbs at three hours a night

Ten 60 watt bulbs, on 3 hours a night, at 17 cents per kilowatt hour, replaced with 9 watt LEDs that cost $3 each.

The old bulbs use 657 kilowatt hours a year. The LEDs use 99. The difference is 558 kilowatt hours, or 85% less, which comes to $94.94 a year at 17 cents. The bulbs cost $30, so payback lands at 3.8 months. Over ten years, after the bulb purchase, the swap nets $919. Per bulb the yearly saving is 55.8 kilowatt hours and $9.49.

That is the ordinary case, and it is why the payback is short even when a bulb costs more than the old one did. The LED also has to last, and here the numbers are comfortable: a bulb rated for 15,000 hours running 3 hours a day covers 13.7 years, which is several times the payback period.

Carbon follows the same math. Using the EPA factor for avoided electricity of 1.48 pounds of CO2 per kilowatt hour, the 558 kilowatt hours saved keep about 827 pounds of CO2 out of the air in a year. That is a rough figure for a national average grid, and it moves with the local fuel mix.

Example: twenty bulbs in a shop or a busy kitchen

Now a harder working set: twenty 100 watt bulbs, on 6 hours a day, in a state where power costs 22 cents, replaced with 15 watt LEDs at $4 each.

The old bulbs draw 4,380 kilowatt hours a year and the LEDs draw 657. The 3,723 kilowatt hour gap is worth $819.06 a year, against $80 for the bulbs. Payback is 1.2 months, and the ten year net after the purchase is $8,111. The CO2 avoided comes to roughly 5,510 pounds a year.

This is the shape of the answer in a workshop, a salon, a small store or a kitchen with a row of cans over the counter. Long hours and a high rate compound, and the bulb price stops mattering. It is also the case where the bulbs are on during the hours the house is air conditioned, so the waste heat from the old bulbs is being paid for twice, once at the meter and once at the thermostat.

How the main bulb types compare

The table below uses the same light output, about 800 lumens, which is what a standard 60 watt incandescent gives you. The yearly cost assumes 3 hours a day at 17 cents per kilowatt hour, so it is a like for like comparison of the technology and not of your habits.

The second table holds everything else fixed at the ten bulb example and changes only the hours per day, because that is the input people guess at worst.

Even the lazy case, one hour a night, pays back inside a year. The catch is that the bulb has to keep working for those ten years, which is why the next section matters.

Where the estimate can go wrong

Cheap bulbs that die early. A $1 bulb that fails in 18 months can cost more than a $4 bulb that runs for a decade, especially in a ceiling fixture where swapping it means dragging out a ladder. Payback assumes the LED reaches its rated hours, and the honest way to protect that assumption is a brand with a real warranty.

Old dimmers. A dimmer built for incandescent loads can make an LED flicker, buzz or fail. If the switch is more than about ten years old, check the dimmer's compatibility list before buying a dozen bulbs.

Heat in winter. An incandescent bulb turns most of its power into heat, roughly 57 watts of heat from a 60 watt bulb, and in a cold month that heat is not wasted, it is just expensive heat. In summer the same heat is a load on the air conditioner, so the real saving is larger in cooling season and smaller in heating season. The calculator gives the year round average, not a month by month breakdown.

Rate tiers and time of use. If your utility charges more in the evening peak, bulbs that run at night save more than the average rate suggests. If you have a flat rate, the default is close enough.

Fixtures with integrated LEDs. Recessed retrofits and strip lights are sold as a unit. The math is the same, but the price per unit is $15 to $40, so enter that price and expect a longer payback.

What to check on the box before you buy

Lumens first. A 60 watt replacement should say about 800 lumens, a 75 watt replacement about 1,100, and a 100 watt replacement about 1,600. Buying on watts alone is how people end up with a bulb that is dimmer than the one it replaced.

Color temperature. 2700 K matches the warm glow of an old incandescent and is the safe choice for living rooms and bedrooms. 3000 K is slightly whiter and works in kitchens. 4000 K and up reads as office light, which is fine in a garage and harsh over a dining table.

Dimmable, if the switch dims. The package states it plainly, and the bulb has to match the dimmer type, not just the socket.

Warranty and the ENERGY STAR mark. The ENERGY STAR technical bulletin on LED lighting notes a three year minimum warranty on certified bulbs and independent testing behind the label. The Department of Energy's LED basics page explains why the same wattage can give different light in different fixtures, since the driver and the fixture design both take a cut.

One last check: count the sockets before you shop. A chandelier with six candelabra sockets is a $30 to $50 swap, and the payback table above does not care whether the bulbs are $2 or $6, only that you enter the real price.