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

About $10.96 a month, assuming 1,100 W at a 80% duty cycle, 8 hours a day, 120 days a year at 15.57¢/kWh.

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

Roughly 845 kWh a year under these assumptions, or 0.88 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 $153 a year.

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

At 15.57¢ per kilowatt-hour — Montana's average residential price in August 2026 — running a portable air conditioner costs $132 a year. That is 14% less than the national average of $153. Montana's residential rate is up 9.0% from August 2025, which moves this appliance from $121 to $132 a year.

Per hour: 13.7¢
Per day of use: $1.10
Per month: $10.96
Per year: $132

Assumption: 1,100 W at a 80% duty cycle, 8 hours a day, 120 days a year — 845 kWh a year. Single-hose portables push conditioned air out of the room and pull unconditioned air in through every crack to replace it, so real-world runtime is longer than the spec sheet implies. 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 $21.88 less a year than the typical U.S. household pays for the same use. Running the same portable air conditioner costs $107 a year in Nevada and $399 in Hawaii, so where you live changes this bill by $291 a year.

State	Rate	Per month	Per year
South Dakota	15.15¢	$10.67	$128
Kansas	15.47¢	$10.89	$131
Montana	15.57¢	$10.96	$132
South Carolina	15.76¢	$11.10	$133
Georgia	15.90¢	$11.19	$134

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

What else costs about the same in Montana

Space heater$135 a year in MT Garage refrigerator$140 a year in MT Electric clothes dryer$121 a year in MT

Cutting the number down

A dual-hose model draws outdoor air for condenser cooling instead of depressurizing your room. It is the biggest efficiency difference in this category.
Insulating the exhaust hose keeps rejected heat from radiating straight back into the room you just cooled.
For the same BTU rating, a window unit almost always costs less to run than a portable.

Questions

How much does a portable air conditioner cost per month in Montana?: About $10.96 a month, assuming 1,100 W at a 80% duty cycle, 8 hours a day, 120 days a year at 15.57¢/kWh.
How many kilowatt-hours does a portable air conditioner use?: Roughly 845 kWh a year under these assumptions, or 0.88 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 $153 a year.