LED bulb savings calculator
Updated
Compare old incandescent bulbs with LED or smart LED bulbs: enter how many, the watts, hours per day and your rate to see the dollars saved per year, kilowatt-hours and payback time.
Next steps
How the calculation works
For each bulb, watts × hours on per day × 365 ÷ 1,000 = kWh per year, then kWh × your rate = dollars. The calculator does that for the old and the new bulbs and subtracts. A smart bulb also draws a small standby power for the hours it is off, which the calculator adds as 0.3 W × (24 minus the hours on).
Example 1 (the default): 10 bulbs, 60 W incandescent replaced by 9 W LEDs, 3 hours a day at 18¢. The old bulbs use 10 × 60 × 3 × 365 ÷ 1,000 = 657 kWh, which is $118.26. The LEDs use about 99 kWh, which is $17.74. Savings: $100.52 a year and about 558 kWh, or 85% less energy. Ten $4 bulbs cost $40, so they pay for themselves in about 4.8 months.
Example 2: 6 smart bulbs at 11 W replacing 75 W incandescents, 4 hours a day, $12 each. Old: 6 × 75 × 4 × 365 ÷ 1,000 = 657 kWh. New: 6 × (11 × 4 + 0.3 × 20) × 365 ÷ 1,000 = about 110 kWh. Saved: about 548 kWh and $98.55 a year (83% less energy); the $72 purchase pays back in roughly 8.8 months.
These results match published figures. The Department of Energy says residential LEDs, especially ENERGY STAR rated ones, use at least 75% less energy and last up to 25 times longer than incandescent lighting. ENERGY STAR says certified bulbs use up to 90% less energy than standard bulbs and about $55 in electricity is saved over a bulb’s lifetime. The default rate of 18¢ per kWh reflects the EIA’s forecast of about 18.2¢ for 2026.
Common mistakes
- Matching watts instead of brightness. Buy by lumens, which are printed on the box, and then compare watts. An LED that is much dimmer than the old bulb saves nothing useful.
- Counting every bulb. The savings come from bulbs that burn for hours. A closet bulb that runs 10 minutes a day will never repay a smart bulb. Start with kitchen, living room and exterior lights.
- Expecting a smart bulb to save more than a standard LED. It saves energy only because it is an LED, and it adds a small standby draw. The benefit is control: schedules, dimming, and turning lights off when you forget. See how to choose smart bulbs.
- Ignoring dimmers. Old dimmers can make LEDs flicker or buzz, so budget for compatible dimmers or smart switches. See smart dimmer and LED flicker.
Frequently asked questions
How much do LED bulbs save compared with incandescent?
The Department of Energy says residential LEDs use at least 75% less energy than incandescent lighting. A 60 W incandescent replaced by a 9 W LED cuts about 85% of the energy at the same hours of use.
Do smart bulbs use power when they are off?
Yes, a small amount, because the radio stays awake to receive commands. It is usually a few tenths of a watt; check the spec sheet. The calculator assumes 0.3 W.
How long until LED bulbs pay for themselves?
At 18¢ per kWh, a $4 LED that replaces a 60 W bulb used 3 hours a day pays back in under 6 months. Smart bulbs at $12 take longer, and they need heavier use to justify the price on energy alone.