Home energy · Lighting
How fast does an LED pay back?
Months to recover the price of LED bulbs from the energy saved, plus the old bulbs you stop buying, using your own watts, hours and rate.
Inputs
Starting values are illustrative, not current prices or specifications. Replace each with your own.
Result
Answer
An LED saves the difference in watts times the hours it is on, at your price per kWh, plus the old bulbs you stop buying. For a 60 W bulb replaced by a 9 W LED on 3 hours a day at $0.15 per kWh, the saving is $9.47 a year and a $3 LED pays back in 3.8 months.
Worked example
Energy saved = (60 − 9) W × 3 h × 365 ÷ 1,000 = 55.8 kWh a year, × $0.15 = $8.38. The old bulb lasts 1,000 hours, so at 1,095 hours a year you buy 1.095 bulbs a year, $1 each = $1.09. Total $9.47 a year. A $3 LED pays back in $3 ÷ $9.47 = 3.8 months. At 30,000 hours the LED lasts 27.4 years, for a net saving of $256.50.
Formulas and notes
- Energy saved per year = (old watts − LED watts) × hours per day × 365 × bulbs ÷ 1,000. Avoided old-bulb cost = hours per year ÷ old bulb life × old bulb price × bulbs. Payback = LED outlay ÷ (energy saving + avoided purchases).
- InterNACHI bulb lives: incandescent 1,000 to 2,000+ hours, halogen 4,000 to 8,000+, compact fluorescent 8,000 to 10,000+, LED 30,000 to 50,000+. This tool starts from the low end of each range. InterNACHI says its figures are guidelines only.
- Cost = kWh × price per kWh (DOE). The LED life is limited by the hours you enter: heat, switching and fixture type can shorten it. Starting values are illustrations.
Planning estimate only, not professional advice. Sources, checked 2026-10-08: U.S. Department of Energy, Estimating Appliance and Home Electronic Energy Use (archived copy, 2024-12-31) · InterNACHI, Standard Estimated Life Expectancy Chart for Homes
FAQ
How long does an LED bulb take to pay for itself?
Divide the LED price by the yearly saving from lower watts and from not buying old bulbs. In the example it is 3.8 months.
How long do LED bulbs last compared with incandescent?
InterNACHI lists LED bulbs at 30,000 to 50,000+ hours and incandescent at 1,000 to 2,000+ hours, as guidelines only.
Does this account for the old bulb I would have bought?
Yes. The avoided purchase is the yearly hours divided by the old bulb's life, times its price.
What if I use the light only a little?
Lower the hours per day. Payback gets longer because less energy is saved, but the LED also lasts more years.
How do I know my LED watts?
It is printed on the bulb or the package.