LED bulb payback calculator

A lower-wattage bulb reduces energy use, but the purchase price determines how long electricity savings take to recover the cost. Compare bulbs with suitable light output and fixture compatibility first.

Replacing working bulbs or buying anyway?

When replacing a working bulb early, enter the full replacement purchase price. If both alternatives require a purchase today, enter only the extra cost of the efficient option. This tool accepts a non-negative cost to recover; if the efficient bulb costs less to buy and run, there is no additional purchase cost to repay.

A transparent six-bulb example

The illustrative difference between 60 W and 9 W is 51 W per bulb. Six bulbs save 306 W while on. At five hours daily, that is 1.53 kWh/day. At $0.18/kWh, daily electricity savings are $0.2754. Six replacements costing $3 each total $18; $18 ÷ $0.2754 ≈ 65.4 days. Annual savings use 365 days at the same schedule and are not a guarantee.

Compare the lighting, not just the watts

Lumens describe light output; watts describe input power. Check the package for brightness, light color, dimmer compatibility and enclosed-fixture suitability. A bulb that does not meet the application is not a useful comparison, even when its calculated cost is lower.

When payback is not reached

With zero use, a zero electricity price, or no wattage reduction, there are no positive electricity savings to recover a purchase cost. A replacement using more power increases modeled energy cost. The tool reports these cases instead of dividing by zero or displaying a misleading negative payback.

Limits of this comparison

Labor, disposal, rebates, financing, replacement frequency and product failures are excluded. Rated lifetime is not a promise about an individual bulb. Rooms used occasionally can have a much longer calendar payback than the five-hour example.

For one billing period, use the LED running-cost comparison. Source: DOE guidance on comparing LED light output.

Method and sources

WattWorth · Published September 17, 2026. AI-assisted educational content; examples are calculated illustrations, not product testing. Editorial approach.

Energy calculations use watts ÷ 1,000 × hours = kWh. U.S. Department of Energy: Electricity 101 · DOE energy education: kWh formula