How much does an LED bulb cost per month?

About 25.1¢ a month at the U.S. average rate, or $3.01 a year.

Where is it cheapest to run?

Nevada, at $2.15 a year, versus $8.66 in Hawaii — a spread of $6.51.

How much does it cost to run an LED bulb?

At the U.S. average residential price of 18.34¢ per kilowatt-hour (June 2026), running an LED bulb costs about $3.01 a year. Your own bill depends on your state's rate, which ranges from 13.11¢ to 52.72¢ across the country.

Per hour: 0.2¢
Per day of use: 0.8¢
Per month: 25.1¢
Per year: $3.01

Assumption: 9 W, 5 hours a day, 365 days a year — 16 kWh a year. A 9 W LED producing about 800 lumens, the equivalent of an old 60 W incandescent.

Cost by state

Same appliance, same usage, 51 different prices. Sorted cheapest first.

State	Rate	Per month	Per year
Nevada	13.11¢	17.9¢	$2.15
Nebraska	13.25¢	18.1¢	$2.18
Utah	13.37¢	18.3¢	$2.20
Louisiana	13.49¢	18.5¢	$2.22
Tennessee	14.07¢	19.3¢	$2.31
North Dakota	14.12¢	19.3¢	$2.32
Arkansas	14.12¢	19.3¢	$2.32
Kentucky	14.26¢	19.5¢	$2.34
Oklahoma	14.33¢	19.6¢	$2.35
Idaho	14.37¢	19.7¢	$2.36
North Carolina	14.74¢	20.2¢	$2.42
Mississippi	14.88¢	20.4¢	$2.44
Washington	14.91¢	20.4¢	$2.45
New Mexico	15.06¢	20.6¢	$2.47
Florida	15.10¢	20.7¢	$2.48
Montana	15.14¢	20.7¢	$2.49
Arizona	15.18¢	20.8¢	$2.49
Wyoming	15.24¢	20.9¢	$2.50
South Dakota	15.36¢	21.0¢	$2.52
West Virginia	15.45¢	21.1¢	$2.54
South Carolina	15.55¢	21.3¢	$2.55
Kansas	15.71¢	21.5¢	$2.58
Iowa	15.93¢	21.8¢	$2.62
Texas	15.94¢	21.8¢	$2.62
Missouri	16.22¢	22.2¢	$2.66
Oregon	16.32¢	22.3¢	$2.68
Georgia	16.36¢	22.4¢	$2.69
Alabama	16.40¢	22.4¢	$2.69
Colorado	17.13¢	23.4¢	$2.81
Virginia	17.22¢	23.6¢	$2.83
Indiana	17.51¢	24.0¢	$2.88
Minnesota	17.52¢	24.0¢	$2.88
Ohio	19.19¢	26.3¢	$3.15
Delaware	19.29¢	26.4¢	$3.17
Wisconsin	19.56¢	26.8¢	$3.21
Illinois	19.89¢	27.2¢	$3.27
Pennsylvania	21.73¢	29.7¢	$3.57
Maryland	21.84¢	29.9¢	$3.59
Michigan	22.99¢	31.5¢	$3.78
Connecticut	24.32¢	33.3¢	$3.99
District of Columbia	24.39¢	33.4¢	$4.01
Vermont	24.44¢	33.5¢	$4.01
New Jersey	24.95¢	34.2¢	$4.10
New Hampshire	27.01¢	37.0¢	$4.44
Alaska	28.21¢	38.6¢	$4.63
Rhode Island	29.23¢	40.0¢	$4.80
New York	29.49¢	40.4¢	$4.84
Maine	29.59¢	40.5¢	$4.86
Massachusetts	29.61¢	40.5¢	$4.86
California	34.74¢	47.6¢	$5.71
Hawaii	52.72¢	72.2¢	$8.66

Cutting the number down

Per bulb the cost is trivial; a house has 40 of them, and that is the number that matters.
Dimming an LED does cut power draw, though not perfectly in proportion to the light output.

Questions

How many watts does an LED bulb use?: About 9 W while running.
How much does an LED bulb cost per month?: About 25.1¢ a month at the U.S. average rate, or $3.01 a year.
Where is it cheapest to run?: Nevada, at $2.15 a year, versus $8.66 in Hawaii — a spread of $6.51.