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?

Louisiana, at $2.09 a year, versus $7.88 in Hawaii — a spread of $5.79.

How much does it cost to run an LED bulb?

At the U.S. average residential price of 18.31¢ per kilowatt-hour (July 2026), running an LED bulb costs about $3.01 a year. Your own bill depends on your state's rate, which ranges from 12.72¢ to 48.00¢ 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
Louisiana	12.72¢	17.4¢	$2.09
Nevada	12.77¢	17.5¢	$2.10
Utah	13.12¢	18.0¢	$2.15
North Dakota	13.41¢	18.4¢	$2.20
Tennessee	13.71¢	18.8¢	$2.25
Idaho	13.73¢	18.8¢	$2.26
Nebraska	13.78¢	18.9¢	$2.26
Kentucky	13.81¢	18.9¢	$2.27
Arkansas	14.33¢	19.6¢	$2.35
Oklahoma	14.35¢	19.6¢	$2.36
Wyoming	14.36¢	19.7¢	$2.36
Mississippi	14.54¢	19.9¢	$2.39
Washington	14.71¢	20.1¢	$2.42
Montana	14.99¢	20.5¢	$2.46
Florida	15.03¢	20.6¢	$2.47
North Carolina	15.16¢	20.8¢	$2.49
Kansas	15.27¢	20.9¢	$2.51
South Dakota	15.37¢	21.0¢	$2.52
Arizona	15.38¢	21.1¢	$2.53
South Carolina	15.47¢	21.2¢	$2.54
West Virginia	15.78¢	21.6¢	$2.59
Texas	15.88¢	21.7¢	$2.61
Oregon	15.97¢	21.9¢	$2.62
Iowa	15.99¢	21.9¢	$2.63
Missouri	16.09¢	22.0¢	$2.64
New Mexico	16.09¢	22.0¢	$2.64
Georgia	16.27¢	22.3¢	$2.67
Alabama	16.40¢	22.4¢	$2.69
Indiana	16.73¢	22.9¢	$2.75
Colorado	17.00¢	23.3¢	$2.79
Minnesota	17.45¢	23.9¢	$2.87
Virginia	17.55¢	24.0¢	$2.88
Delaware	18.48¢	25.3¢	$3.04
Wisconsin	19.06¢	26.1¢	$3.13
Illinois	19.22¢	26.3¢	$3.16
Ohio	19.45¢	26.6¢	$3.19
Maryland	21.41¢	29.3¢	$3.52
Pennsylvania	21.72¢	29.7¢	$3.57
Michigan	23.05¢	31.5¢	$3.79
Vermont	23.75¢	32.5¢	$3.90
Connecticut	24.16¢	33.1¢	$3.97
New Jersey	25.19¢	34.5¢	$4.14
District of Columbia	25.21¢	34.5¢	$4.14
New Hampshire	26.60¢	36.4¢	$4.37
Rhode Island	28.29¢	38.7¢	$4.65
Alaska	28.83¢	39.5¢	$4.74
New York	29.90¢	40.9¢	$4.91
Massachusetts	30.49¢	41.7¢	$5.01
Maine	32.41¢	44.4¢	$5.32
California	33.61¢	46.0¢	$5.52
Hawaii	48.00¢	65.7¢	$7.88

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?: Louisiana, at $2.09 a year, versus $7.88 in Hawaii — a spread of $5.79.