Lightbulb Replacement Calculator. Enter details about your current lightbulb and replacement bulb — including wattage, bulb cost, rated life (hours), hours used per week, and your electricity rate — and this Lightbulb Replacement Calculator shows you when each bulb needs replacing, how much you spend on energy and replacements, and exactly how much you'll save by switching. Also try the Oil Change Interval Calculator.
The rated life in hours is printed on the bulb's packaging or sometimes on the bulb itself. Common values are 1,000 hours for incandescent bulbs, 8,000–10,000 hours for CFLs, and 15,000–25,000 hours for LED bulbs. You can also check the manufacturer's website using the bulb model number. See also our Expiration Date Calculator.
The replacement interval is your bulb's rated life in hours divided by the number of hours you use it per week. For example, a 1,000-hour bulb used 35 hours per week will need replacing roughly every 28.6 weeks (about 7 months).
The annual cost includes three components: energy cost (wattage × hours used per year × electricity rate), bulb purchase cost (prorated over the number of replacements needed per year), and labor cost (time to replace × labor rate × number of replacements per year). Adding all three gives a true total cost of ownership.
LED bulbs consume significantly less wattage — typically 8–10W versus 60W for an equivalent incandescent — and last up to 25 times longer. While the purchase price is higher, the energy savings and fewer replacements (including labor) result in dramatically lower total annual costs, usually paying back the upfront cost within months.
Use the rate shown on your electricity bill, typically expressed as cents per kilowatt-hour (kWh). The US average is around $0.13/kWh, but rates vary significantly by state and provider. Check your most recent bill for the most accurate figure.
If you replace bulbs yourself, set the labor cost to $0. However, for commercial or hard-to-reach installations where a professional electrician or maintenance worker changes bulbs, including a realistic labor rate gives a much more accurate picture of the true cost of your current lighting setup.
Enter the total number of fixtures or sockets you are evaluating. You can run the calculator for a single bulb to compare on a per-unit basis, or enter your full home or building count to see the total annual savings across all fixtures.
The payback period is how long it takes for the savings from the new bulb to offset its higher upfront cost. A payback period of a few months means switching is a no-brainer; anything under two years is generally considered a smart investment for lighting upgrades. You might also find our calculate Estimated Remaining Miles, Months Until Replacement & Tread Life Used — Tire Life useful.