How much does an aquarium cost per month in Montana?

About $7.39 a month, assuming 150 W at a 45% duty cycle, 24 hours a day, 365 days a year at 14.99¢/kWh.

How many kilowatt-hours does an aquarium use?

Roughly 591 kWh a year under these assumptions, or 0.07 kWh for every hour it runs.

Is that expensive compared with other states?

Montana has the 14th cheapest average residential rate in the country, so this appliance costs less here than the U.S. average of $108 a year.

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Cost to run an aquarium in Montana (July 2026 rates)

At 14.99¢ per kilowatt-hour — Montana's average residential price in July 2026 — running an aquarium costs $88.64 a year. That is 18% less than the national average of $108. Montana's residential rate is up 5.0% from July 2025, which moves this appliance from $84.38 to $88.64 a year.

Per hour: 1.0¢
Per day of use: 24.3¢
Per month: $7.39
Per year: $88.64

Assumption: 150 W at a 45% duty cycle, 24 hours a day, 365 days a year — 591 kWh a year. A 55-gallon tank: heater, filter and light combined, averaged over a day. Use the calculator to swap in the numbers from your own model.

How Montana compares

Montana pays 14.99¢/kWh, the 14th cheapest residential electricity of the 51 U.S. jurisdictions EIA reports. For this appliance that works out to $19.63 less a year than the typical U.S. household pays for the same use. Running the same aquarium costs $75.21 a year in Louisiana and $284 in Hawaii, so where you live changes this bill by $209 a year.

State	Rate	Per month	Per year
Mississippi	14.54¢	$7.16	$85.98
Washington	14.71¢	$7.25	$86.98
Montana	14.99¢	$7.39	$88.64
Florida	15.03¢	$7.41	$88.87
North Carolina	15.16¢	$7.47	$89.64

States ranked by average residential price, cheapest first. See all 51 states for an aquarium.

What else costs about the same in Montana

Gaming pc$87.54 a year in MT Well pump$82.07 a year in MT Dehumidifier$80.95 a year in MT

Cutting the number down

The heater is nearly all of it, and its runtime depends on the room. A tank in a cool room costs more to keep warm.
Insulating the back and sides of the tank cuts heater runtime without changing the view.
A lid limits evaporative heat loss, which is the main way an open tank sheds the warmth you paid for.

Questions

How much does an aquarium cost per month in Montana?: About $7.39 a month, assuming 150 W at a 45% duty cycle, 24 hours a day, 365 days a year at 14.99¢/kWh.
How many kilowatt-hours does an aquarium use?: Roughly 591 kWh a year under these assumptions, or 0.07 kWh for every hour it runs.
Is that expensive compared with other states?: Montana has the 14th cheapest average residential rate in the country, so this appliance costs less here than the U.S. average of $108 a year.