Running cost comes down to wattage, hours and your rate. In Illinois the rate is 23.85 cents per kWh, which is 29.3 percent above the national average. Here is what that means for a central air conditioner.
A central air conditioner drawing 3,500 W costs $0.83 per hour in Illinois. Run 8 hours a day that is $6.68 daily, $200 a month and $2,437 a year, which is $553 more than the same appliance at the US average rate.
Cost by hours used per day in Illinois
| Hours/day | Energy | Per day | Per month |
|---|---|---|---|
| 1 h | 3.50 kWh | $0.83 | $25.04 |
| 2 h | 7.00 kWh | $1.67 | $50.09 |
| 4 h | 14.00 kWh | $3.34 | $100 |
| 6 h | 21.00 kWh | $5.01 | $150 |
| 8 h | 28.00 kWh | $6.68 | $200 |
| 12 h | 42.00 kWh | $10.02 | $301 |
| 24 h | 84.00 kWh | $20.03 | $601 |
Cost by wattage at 23.85 cents
| Rated power | Per hour | Per day | Per month |
|---|---|---|---|
| 2,000 W | $0.48 | $3.82 | $114 |
| 2,500 W | $0.60 | $4.77 | $143 |
| 3,000 W | $0.72 | $5.72 | $172 |
| 3,500 W | $0.83 | $6.68 | $200 |
| 5,000 W | $1.19 | $9.54 | $286 |
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 Illinois
Illinois sits in the middle band for cooling demand, typically three to four months of real use. The annual figure therefore lands well below the twelve-month projection, and shoulder-season months often need only intermittent operation.
Why Illinois pays what it does
Illinois has a competitive retail electricity market, so the rate used here blends households on the utility default with households on shopped supply plans. If you have never switched supplier you are probably on the default, which is usually the more expensive side of that blend. Only the generation portion of your bill changes when you switch; delivery and outage response do not.
At 23.85 cents, Illinois ranks 40 of 51 from cheapest to most expensive. The Midwest regional average is 16.55 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 |
| Illinois | 23.85¢ | $200 | $2,437 |
| California | 33.25¢ | $279 | $3,398 |
| Hawaii | 52.00¢ | $437 | $5,314 |
Lowering the number in Illinois
- 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 Illinois
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 23.85 cents rather than the national 18.44 cents, the same array is worth more 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.
Questions people actually ask
[hed_faq]How much does it cost to run a central air conditioner in Illinois?About $0.83 per hour and $200 a month at 8 hours a day, using the Illinois average rate of 23.85 cents per kWh.
How many watts does a central air conditioner use?Around 3,500 W while running, with a range of roughly 1,500 to 5,000 W depending on model and setting.
Is that expensive for Illinois?Illinois electricity runs 29.3 percent above the national average, so this appliance costs $553 more per year here than it would at the US average rate.
Can I lower this without replacing the appliance?Usually yes. Run time is the variable you control, and the hours table above shows exactly what each hour costs. In Illinois you can also shop for a cheaper supply rate, which lowers every figure on this page proportionally.[/hed_faq]