Running cost comes down to wattage, hours and your rate. In Montana the rate is 14.67 cents per kWh, which is 20.4 percent below the national average. Here is what that means for a central air conditioner.
A central air conditioner drawing 3,500 W costs $0.51 per hour in Montana. Run 8 hours a day that is $4.11 daily, $123 a month and $1,499 a year, which is $385 less than the same appliance at the US average rate.
Central air conditioner cost at Montana rates
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Planning estimate. The rate box is prefilled with a regional average; the figure on your own bill is the one that matters. Power is draw while running, not while switched on.
Cost by hours used per day in Montana
| Hours/day | Energy | Per day | Per month |
|---|---|---|---|
| 1 h | 3.50 kWh | $0.51 | $15.40 |
| 2 h | 7.00 kWh | $1.03 | $30.81 |
| 4 h | 14.00 kWh | $2.05 | $61.61 |
| 6 h | 21.00 kWh | $3.08 | $92.42 |
| 8 h | 28.00 kWh | $4.11 | $123 |
| 12 h | 42.00 kWh | $6.16 | $185 |
| 24 h | 84.00 kWh | $12.32 | $370 |
Cost by wattage at 14.67 cents
| Rated power | Per hour | Per day | Per month |
|---|---|---|---|
| 2,000 W | $0.29 | $2.35 | $70.42 |
| 2,500 W | $0.37 | $2.93 | $88.02 |
| 3,000 W | $0.44 | $3.52 | $106 |
| 3,500 W | $0.51 | $4.11 | $123 |
| 5,000 W | $0.73 | $5.87 | $176 |
Find the row matching the nameplate on your own unit. Within a single appliance category the spread is often wider than the difference between categories, so the label is worth reading.
Cooling season in Montana
Cooling season in Montana is short, often eight to ten weeks of genuine demand. That limits the annual figure sharply, and it also changes the economics of equipment: a high-efficiency system has fewer hours over which to recover its price premium here than it would in the South.
Why Montana pays what it does
Montana is a regulated market, so your utility is the only supplier and the rate is set through the state commission rather than by competition. Pricing tends to be steadier than in deregulated states, and there is no switching decision available. The levers are all on your side of the meter.
At 14.67 cents, Montana ranks 13 of 51 from cheapest to most expensive. The West regional average is 19.65 cents. Roughly half of any residential bill is transmission and distribution rather than generation, which is why rates keep climbing even when fuel prices fall.
How this compares across the country
The same central air conditioner on the same schedule, in the cheapest and dearest states:
| State | Rate | Per month | Per year |
|---|---|---|---|
| Idaho | 12.35¢ | $104 | $1,262 |
| Utah | 12.96¢ | $109 | $1,325 |
| Montana | 14.67¢ | $123 | $1,499 |
| California | 33.25¢ | $279 | $3,398 |
| Hawaii | 52.00¢ | $437 | $5,314 |
Lowering the number in Montana
- Raise the thermostat before anything else. Each degree warmer cuts compressor runtime, and runtime is the entire cost. Going from 70 to 74 commonly reduces cooling energy by a fifth or more.
- Change the filter every one to three months. Restricted airflow lengthens every cycle and strains the blower.
- Seal and insulate ducts. Duct losses in an unconditioned attic routinely waste 20 to 30 percent of what the system produces.
- Run ceiling fans alongside it. A fan costs roughly a cent an hour and lets most people sit comfortably three degrees warmer.
- Shade the condenser, not the airflow. A unit in direct sun works harder, but blocking airflow around it makes things worse.
Offsetting it with solar in Montana
This load uses about 28.00 kWh a day. Covering that would take roughly 20 standard 400 W panels at typical sun hours, an array of about 8.00 kW. Because it offsets electricity worth 14.67 cents rather than the national 18.44 cents, the same array is worth less here than the national payback figures suggest.
A central system is a large enough load that it usually determines the size of the whole array rather than being an add-on to it. Full sizing, including battery and inverter requirements, is on the solar sizing page for this appliance.