Appliance Cost Lab

LED-bulb guide

How much electricity does one LED light bulb use?

For an ordinary switched bulb, multiply its electrical input watts by the hours it is illuminated and your electricity rate.

This guide models one bulb. For several identical bulbs with the same schedule, use calculator quantity. Measure or calculate different bulb wattages and schedules separately.

Three single-bulb scenarios

Three published LED light-bulb electricity-cost scenarios
Scenario Visible inputs Annual energy Annual cost
6 W for three daily hours One bulb; 6 W; 3 h/day; 7 days/week; 100% duty; 0 W standby; $0.18/kWh 6.570 kWh $1.18
9 W for five daily hours One bulb; 9 W; 5 h/day; 7 days/week; 100% duty; 0 W standby; $0.18/kWh 16.425 kWh $2.96
12 W for eight daily hours One bulb; 12 W; 8 h/day; 7 days/week; 100% duty; 0 W standby; $0.18/kWh 35.040 kWh $6.31

$0.18/kWh is an illustrative comparison rate, not a national or current market price. No scenario is a claim about a common LED wattage.

Calculation and quantity

annual kWh for one bulb = input watts × illuminated hours/day × 365 ÷ 1000

For four identical bulbs that truly use the same watts and schedule, quantity four multiplies energy and cost by four. Do not group bulbs with different labels, dimming, occupancy, or schedules under one input.

Ordinary and connected bulbs

The ordinary-bulb reference uses zero standby because a wall switch disconnects its input. A connected or smart bulb—or its hub—can consume idle power while available for network control. Enter or measure that idle consumption separately; active watts do not measure it automatically.

Confirmation is required before any smart-plug or scheduled-disconnection evaluation. The site cannot identify the lamp, controls, load, electrical ratings, or connected functions that must remain available.

Use input watts from the bulb label, not an incandescent-equivalent marketing number or lumen output. A compatible meter can replace the illustrative input where the lamp and equipment instructions allow measurement.

Calculate your LED-bulb cost

Sources: ENERGY STAR LED guidance explains LED operation and the distinction between light output and electrical technology; DOE light-bulb purchasing guidance supports checking product specifications. Neither validates these wattages.

Related: standby-power guide · methodology · accuracy guide · data sources

Last reviewed: August 14, 2026