How much does switching to LED save?

What the number tells you

Replacing a bulb has two kinds of benefit. The first is electricity: an incandescent bulb turns most of its power into heat, and the Department of Energy says an ENERGY STAR certified LED uses up to 90% less energy to give the same light. The second is fewer bulbs to buy, because an LED is rated for 15 to 25 times the life of an old bulb. This calculator adds both, divides the price of the LED by the yearly total to get a simple payback, and multiplies the yearly total by the LED's life in years to show what you keep after paying for it. The U.S. Energy Information Administration's 2024 housing survey (preliminary) found that 90% of US homes already use LED bulbs, and 37% use them for all indoor lighting, so the question for most households is the last few old bulbs, usually in the rooms where lights burn longest.

The method

For each bulb: kWh a year = watts × hours a day × 365 ÷ 1,000 × number of bulbs. Electricity cost = kWh × price. Old bulbs not bought = hours a year ÷ old bulb life × price. Yearly saving = electricity saved + old bulbs not bought. Payback (years) = LED price × number of bulbs ÷ yearly saving. Lifetime saving = yearly saving × (LED life ÷ hours a year) − LED price. The "years of life" depends on the hours: 25,000 hours is 22.8 years at 3 hours a day but only about 6.8 years at 10 hours.

Worked example

One 60-watt incandescent replaced by a 9-watt LED, 3 hours a day, 17.23¢ per kWh. The old bulb uses 65.7 kWh a year and costs $11.32; the LED uses 9.9 kWh and costs $1.70. Electricity saved: 55.8 kWh, $9.62. With a 1,000-hour old bulb at $1 you also skip 1.1 bulbs a year, $1.10. Together $10.72 a year; a $3 LED pays for itself in 3.4 months and, over its 22.8-year life, leaves $241.68. For comparison, the federal table gives an 800-lumen ENERGY STAR LED (11 W) a yearly energy use of 43 kWh and a less efficient 18 W bulb 70 kWh at 10.7 hours a day and 9.9¢; the calculator reproduces those figures, and the "best available" 5.5 W LED comes to 21.5 kWh.

Limits and common mistakes

• Comparing watts instead of lumens. Many LED "60-watt equivalents" differ in brightness. DOE FEMP lists LED bulbs of 800 lumens from 5.9 to 10.5 watts, a 40% spread, so the efficiency of the specific bulb changes the saving. Read the Lighting Facts label.
• Overestimating the hours. The Lighting Facts label assumes 3 hours a day; the federal-building table assumes 10.7. Most home lights burn far fewer hours than people think, and payback scales inversely with hours.
• Ignoring heating and cooling. An old bulb's wasted heat warms the room a little in winter and adds to cooling in summer. This calculator counts electricity for lighting only.
• Rated life is not guaranteed life. It is a rating under test conditions, and ENERGY STAR defines LED life as the point when light output has dropped by 30%. DOE notes that bulbs last their full rated life when installed in efficient fixtures.
• Sample prices. The $1 and $3 in the form are placeholders, not market data.

How much do LED bulbs save compared with incandescent?

The Department of Energy says an ENERGY STAR certified LED uses up to 90% less energy than an old incandescent bulb and lasts 15 to 25 times longer. The exact saving is your watts difference times hours times price. A 60-watt incandescent replaced by a 9-watt LED, on 3 hours a day at 17.23 cents per kWh, saves 56 kWh and $9.62 of electricity a year, plus the 1.1 old bulbs a year you no longer buy. Ten such bulbs save $107.17 a year. The result scales with hours: the same bulb used 1 hour a day saves $3.57.

How many watts is an LED equal to a 60-watt bulb?

Look at lumens, not watts. ENERGY STAR and the Department of Energy treat about 800 lumens as the replacement for a 60-watt incandescent, 450 lumens for 40 watts, 1,100 for 75 watts and 1,600 for 100 watts. In the DOE FEMP bulb guidance (June 2023) LED bulbs of 800 lumens use 5.9 to 10.5 watts, 450 lumens 4.5 to 7 watts, 1,100 lumens 9.5 to 14 watts and 1,600 lumens 10.5 to 18 watts. Our default of 9 watts sits inside the 800-lumen range. Use the figure printed on the package of the LED you plan to buy.

How long does an LED bulb really last?

DOE's federal guidance uses a rated life of 25,000 hours, the minimum ENERGY STAR sets for LED bulbs. At 3 hours a day that is 22.8 years, the same number as on a sample Lighting Facts label in DOE's Energy Saver Guide. At 10.7 hours a day, the federal-building assumption, it is about 6.4 years. LED life is the point where light output drops by 30%, not the day the bulb goes dark (ENERGY STAR), so a bulb can keep working after its rated hours. DOE notes that efficient bulbs last their maximum lifetime when installed in efficient fixtures.

What is the payback of switching to LED?

Simple payback is the price of the LED divided by what you save each year. With the placeholder prices of $1 for the old bulb and $3 for the LED, one bulb at 3 hours a day pays back in about 3 months. Real prices differ, and hours matter most: a bulb that burns 1 hour a day pays back in about 10 months, and one that burns 10 hours a day in a matter of weeks. Put the price from the shelf and your own hours into the calculator. If you already own the old bulbs, swap them only when they burn out or when the room is used many hours a day.

Should I replace working incandescent or CFL bulbs now?

Usually yes for bulbs that burn several hours a day, because the electricity saving alone pays for the LED in months. For a closet light used ten minutes a day, wait until the old bulb fails. FEMP's June 2023 guidance notes that the ENERGY STAR database lists just one CFL in this class. The calculator works for any old bulb: type its watts and its rated life from the package. Halogen and CFL watts for the same lumens are on the box; we do not guess them here.

Do LEDs work with dimmers, and does it affect savings?

Many LED bulbs are dimmable, but not all, and an old dimmer can make a new LED flicker or hum. The Department of Energy's guide says to check the package to make sure the bulb works with dimmers, daylight sensors or motion sensors. If you usually run a bulb dimmed, enter the watts it really draws at that setting (a plug-in watt meter shows it).

Sources: U.S. Department of Energy, Federal Energy Management Program, Purchasing Energy-Efficient Light Bulbs (Tables 1 and 2; updated June 2023); U.S. Department of Energy, Energy Saver Guide 2022 (Lighting, Lighting Facts label); U.S. EIA, Residential Energy Consumption Survey 2024 (preliminary housing characteristics) and Electric Power Annual 2025, Table 2.4; ENERGY STAR, Learn about LED bulbs. Related tools: lumens to watts calculator, electricity cost calculator, standby power cost calculator, room lumens calculator. How we check our calculators.