How much does a central air conditioner cost per month in Montana?

About $30.52 a month, assuming 3,500 W at a 70% duty cycle, 8 hours a day, 120 days a year at 15.57¢/kWh.

How many kilowatt-hours does a central air conditioner use?

Roughly 2,352 kWh a year under these assumptions, or 2.45 kWh for every hour it runs.

Is that expensive compared with other states?

Montana has the 19th cheapest average residential rate in the country, so this appliance costs less here than the U.S. average of $427 a year.

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Cost to run a central air conditioner in Montana (August 2026 rates)

At 15.57¢ per kilowatt-hour — Montana's average residential price in August 2026 — running a central air conditioner costs $366 a year. That is 14% less than the national average of $427. Montana's residential rate is up 9.0% from August 2025, which moves this appliance from $336 to $366 a year.

Per hour: 38.1¢
Per day of use: $3.05
Per month: $30.52
Per year: $366

Assumption: 3,500 W at a 70% duty cycle, 8 hours a day, 120 days a year — 2,352 kWh a year. A 3-ton central system draws roughly 3,500 W with the air handler running. Older or oversized units cycle harder and land higher. Use the calculator to swap in the numbers from your own model.

How Montana compares

Montana pays 15.57¢/kWh, the 19th cheapest residential electricity of the 51 U.S. jurisdictions EIA reports. For this appliance that works out to $60.92 less a year than the typical U.S. household pays for the same use. Running the same central air conditioner costs $299 a year in Nevada and $1,110 in Hawaii, so where you live changes this bill by $810 a year.

State	Rate	Per month	Per year
South Dakota	15.15¢	$29.69	$356
Kansas	15.47¢	$30.32	$364
Montana	15.57¢	$30.52	$366
South Carolina	15.76¢	$30.89	$371
Georgia	15.90¢	$31.16	$374

States ranked by average residential price, cheapest first. See all 51 states for a central air conditioner.

What else costs about the same in Montana

Hot tub$389 a year in MT Heat pump$336 a year in MT Pool pump$269 a year in MT

Cutting the number down

Each degree you raise the thermostat in summer trims roughly 3% off cooling energy. Two degrees is a rounding error in comfort and a visible line on the bill.
A clogged filter makes the blower work against restriction for an entire season. Replacing it is the cheapest maintenance in the house.
Cooling load tracks the indoor/outdoor gap, so the same thermostat setting costs far more in a 100 F week than an 85 F one.

Questions

How much does a central air conditioner cost per month in Montana?: About $30.52 a month, assuming 3,500 W at a 70% duty cycle, 8 hours a day, 120 days a year at 15.57¢/kWh.
How many kilowatt-hours does a central air conditioner use?: Roughly 2,352 kWh a year under these assumptions, or 2.45 kWh for every hour it runs.
Is that expensive compared with other states?: Montana has the 19th cheapest average residential rate in the country, so this appliance costs less here than the U.S. average of $427 a year.