LED Savings Calculator: What Switching Bulbs Saves

LED bulbs make the same light as old incandescent bulbs with a fraction of the electricity. The savings per bulb are small, but across a whole house, and over years, they are one of the quickest paybacks in home energy. This calculator shows how quickly yours pay off.

How the calculation works

The calculator finds the watts you save per bulb, multiplies by how long the lights are on, and turns that into kWh and dollars.

Watts saved          = old bulb watts − LED watts
kWh saved per year   = bulbs × watts saved × hours per day × 365 ÷ 1,000
Savings per year     = kWh saved × electricity price ($/kWh)
Cost of new bulbs    = bulbs × price per LED
Payback (months)     = cost of new bulbs ÷ savings per year × 12

The default electricity price is $0.18 per kWh, from the US average residential price of 18.31 cents per kWh in July 2026 (EIA, Table 5.6.A). The default LED is 9 watts, a common draw for a bulb that matches a 60-watt incandescent (about 800 lumens, per University of Maryland Extension). The $3 bulb price is a placeholder; use what you actually pay.

The calculator assumes each light is on the same number of hours every day of the year, and that the LED gives similar light. It does not count the cost of old bulbs you would otherwise buy.

Worked example

The default inputs: 15 bulbs, old bulbs at 60 watts, LEDs at 9 watts, on 3 hours a day, at $0.18 per kWh, with LEDs at $3 each.

1. Watts saved per bulb: 60 − 9 = 51 watts.
2. Energy saved: 15 × 51 W × 3 hours × 365 days ÷ 1,000 = 838 kWh a year.
3. Money saved: 838 kWh × $0.18 = about $151 a year.
4. Cost of bulbs: 15 × $3 = $45.
5. Payback: $45 ÷ $151 × 12 = about 4 months.

A second example

Say you have 8 old 100-watt bulbs in a kitchen and family room that are on 5 hours a day. You replace them with 15-watt LEDs at $5 each, and pay $0.16 per kWh. The calculator shows 1,241 kWh saved, about $199 a year, $40 for the bulbs and a payback of about 2 months.

Compare that with a closet or guest room: 15 bulbs on only half an hour a day, with the other defaults unchanged, save just 140 kWh and about $25 a year, with a payback of about 21 months. Same bulbs, very different value.

What your result means

• Payback under a year: replace these bulbs now. Few home upgrades pay back faster.
• Payback of one to three years: still worthwhile, especially as the old bulbs burn out.
• Payback longer than that: these lights are rarely on. Replace them when they fail.

The yearly savings figure repeats every year the LED keeps working. University of Maryland Extension says LEDs typically last 15,000 to 25,000 hours, so a bulb used 3 hours a day can keep saving for well over a decade.

How hours of use change your savings

This table uses the calculator’s defaults (15 bulbs, 60 W to 9 W, $0.18 per kWh, $3 per LED) and changes only the hours per day.

If your old bulbs are not 60-watt incandescents, enter the wattage printed on the bulb. For example, swapping 15 bulbs of 43 watts for 9-watt LEDs, with the other defaults, saves about 558 kWh and $101 a year, with a payback of about 5 months.

Rules and local factors that change the answer

Federal lighting rules. The Department of Energy requires general service bulbs to meet a minimum of 45 lumens per watt and has said it will pursue penalties for bulbs that do not (DOE guidance, October 2022). University of Maryland Extension notes that this effectively ended sales of most incandescent and halogen bulbs, with enforcement beginning in 2023. So this calculator is mostly about the old bulbs still in your sockets.

ENERGY STAR labels on bulbs. University of Maryland Extension reports that EPA ended ENERGY STAR certification for most lamps and fixtures at the end of 2024, because LEDs had become the norm. Many bulbs will no longer carry the label. Use the FTC Lighting Facts label on the box to compare lumens, watts, life and yearly cost.

Your electricity rate. At the July 2026 averages from EIA, the default 838 kWh saved is worth much more in a high-price state like California (33.61 cents per kWh) than in a lower-price state like Louisiana (12.72 cents). Enter your own rate.

Utility programs. Some utilities still offer discounted bulbs or free kits. If energy costs are a strain, our guide to help paying energy bills lists programs that can help. Search DSIRE or your utility’s site. For a ranked list of other low-cost fixes, see our guide on how to lower your energy bill.

Common mistakes

• Matching watts instead of lumens. A “9-watt” LED is not dim. Shop by lumens: about 800 lumens replaces a 60-watt bulb.
• Overestimating hours. Most bulbs are on less than you think. Guess low if unsure.
• Counting fixtures that are already LED. Many homes are partly converted. Count only the old bulbs.
• Ignoring fixture type. Use bulbs rated for enclosed fixtures or dimmers where needed. The wrong bulb can flicker or fail early.
• Using the energy rate only. Your all-in price per kWh, including fees and taxes, is a fairer number. The electric bill calculator shows it.

Limits of this calculator

The calculator assumes constant daily use and a flat electricity rate. It does not include the small effect of bulb heat on heating and cooling, the cost of replacement bulbs you avoid buying, or differences in light quality between bulbs. Real LED wattage varies by product.

It gives an educational estimate, not a quote or advice. If you are doing a broader check of where your home’s electricity goes, a home energy audit and the phantom load calculator help find the rest.