LED Bulb Savings Calculator

Enter the number of bulbs you are switching, the old and new wattage, the hours each fixture is on per day, your electricity rate, and the price of each bulb type. Rated life defaults to 15,000 hours for the LED and 1,000 hours for the incandescent. Change both to the hours printed on your packaging.

Worked example: 10 bulbs, 60 W to 9 W, 4 hours a day, $0.1883/kWh, $5 per LED and $1 per incandescent. Each bulb saves 51 W, so the ten save 744.6 kWh a year, worth $140.21.

At 1,460 hours a year, each incandescent socket needs about 1.46 new bulbs a year, while an LED needs about 0.097. That gap is worth another $9.73. Total savings: $149.94 a year, or $12.50 a month.

The upfront premium is 10 × ($5 − $1) = $40, which pays back in 3.2 months. At 4 hours a day a 15,000-hour LED lasts 10.3 years, and the calculator puts lifetime net savings at $1,500.49.

Watts saved per bulb = Old watts − New watts.

Annual kWh saved = Watts saved × Hours per day × 365 ÷ 1,000 × Number of bulbs. Energy savings = Annual kWh saved × Electricity rate.

Replacements per year = (Hours per day × 365) ÷ Rated life hours, worked out separately for each bulb type. Replacement savings = (Incandescent replacements × Incandescent price − LED replacements × LED price) × Number of bulbs.

Total annual savings = Energy savings + Replacement savings. Upfront premium = (LED price − Incandescent price) × Number of bulbs, never below zero.

Payback (months) = Upfront premium ÷ Total annual savings × 12. LED life (years) = LED rated hours ÷ (Hours per day × 365). Lifetime net savings = Total annual savings × LED life in years − Upfront premium.

A whole house is mostly fixtures that are on for less time than the living room. Take 25 bulbs at 60 W to 9 W, averaging 3 hours a day, with the same prices and rate.

The house saves 1,396.1 kWh a year, worth $262.89 in electricity, plus $18.25 in replacement bulbs. That makes $281.14 a year, or $23.43 a month. The $100 premium pays back in 4.3 months.

Fewer daily hours mean each LED lasts longer, 13.7 years, so lifetime net savings reach $3,751.24.

Compare this with the single bulb in the Quick Answer. Per bulb, the house saves less each year, because 3 hours of use saves less than 4. But the payback only stretches from 3.2 to 4.3 months. Hours per day moves the answer much more than the number of bulbs does.

Wattage measures power drawn, not brightness. Brightness is lumens. ENERGY STAR's brightness guide gives the minimum lumens that replace an old incandescent: 40 W → 450 lumens, 60 W → 800, 75 W → 1,100, 100 W → 1,600, 150 W → 2,600. The FTC's consumer guide gives an 800-lumen LED as drawing about 9 W, which is why this calculator defaults to 9 W.

To use the table, look up the old bulb's wattage, find an LED with at least that many lumens, and enter the LED's actual wattage in the New LED field. The package's Lighting Facts label shows lumens, wattage, estimated yearly energy cost, expected life in years, and light appearance (warm or cool).

Common mistake: entering the "60 W equivalent" figure as the new wattage. That makes watts saved zero, and the calculator will show no energy saving at all.

A single high-use bulb: 100 W to 14 W, on 6 hours a day, with a $6 LED against a $1.50 incandescent. It saves 188.3 kWh and $37.87 a year, and the $4.50 premium pays back in 1.4 months. The same swap at 4 hours a day saves $25.25 and takes 2.1 months. Heavy use also wears the LED out sooner: at 6 hours a day, 15,000 hours lasts 6.8 years.

A house that is already mostly LED: since 2023, federal efficiency standards for general service lamps have set a minimum of 45 lumens per watt. Standard incandescent bulbs cannot meet it, so many homes have already switched most sockets. If 5 incandescent sockets are left at 3 hours a day, enter 5 bulbs. They are worth $56.23 a year with a 4.3-month payback. That is still an easy win, but the total is a fraction of the whole-house figure.

Replacing a working LED with a newer one rarely pays. Going from 9 W to 7 W at 3 hours a day saves 2.19 kWh, or $0.41 a year, so a $5 bulb takes about 12 years to pay back on energy alone. The calculator's replacement line is built for incandescent lifetimes, so for an LED-to-LED swap, read only the energy savings.

The model assumes a flat electricity rate and the same hours every day of the year. Seasonal lights, time-of-use tariffs and fixtures on timers will differ.

It ignores heat. Incandescent bulbs give off waste heat, which adds a little to air-conditioning load in summer and offsets a little heating in winter, so real savings differ slightly by climate.

Rated life is treated as a straight line. Enclosed fixtures, heat and frequent switching can shorten an LED's life, and dimmers need compatible bulbs. Utility rebates are not included: if you get one, lower the LED price you enter.

Lighting is a small share of most bills. EIA's 2020 Residential Energy Consumption Survey put lighting at about 6% of household electricity use. A fast payback here does not add up to large savings on the total bill.

Lighting runs only while a switch is on. Standby loads draw power around the clock. The vampire power drain calculator adds up what idle electronics cost you, and the smart power strip calculator shows what cutting those loads automatically is worth.

The same watts-times-hours method works for any plug-in device in the appliance energy calculator. For larger upgrades, the Energy Star appliance savings calculator runs a similar payback test on refrigerators and washers, and the home energy audit calculator shows how lighting fits within the whole bill.