When summer heat settles into Chicago, your air conditioner can quickly become one of the hardest-working systems in your home. It can also become one of the biggest reasons your electric bill goes up. If you are wondering how much it costs to run an air conditioner, the answer depends on your system type, electricity rate, home size, thermostat setting, and how often your AC runs.
As Chicago’s trusted air conditioning experts since 1922, Deljo Heating, Cooling & Plumbing helps homeowners understand what affects cooling costs and how to keep their homes comfortable without wasting energy. Below, we break down the average cost to run AC, how to estimate your own usage, and practical ways to lower your AC bill.
Quick Answer: How Much Does It Cost to Run AC?
The cost to run AC depends on how much electricity your system uses and how long it runs each day. A small window AC unit may cost less to operate than central AC, but it only cools one room. Central AC usually costs more overall because it cools the entire home.
Using an example electricity rate of $0.16 per kWh, estimated AC running costs may look like this:
| AC Type | Estimated Power Use | Cost Per Hour | Cost Per Day, 8 Hours | Cost Per Month, 8 Hours/Day |
| Small window AC unit | 500–800 watts | $0.08–$0.13 | $0.64–$1.02 | $19–$31 |
| Large window AC unit | 1,000–1,500 watts | $0.16–$0.24 | $1.28–$1.92 | $38–$58 |
| Ductless mini-split | 600–2,000 watts | $0.10–$0.32 | $0.77–$2.56 | $23–$77 |
| Central AC system | 3,000–5,000 watts | $0.48–$0.80 | $3.84–$6.40 | $115–$192 |
| Portable AC unit | 1,000–1,500 watts | $0.16–$0.24 | $1.28–$1.92 | $38–$58 |
These numbers are only examples. Your actual air conditioner running cost may be higher or lower depending on your utility rate, system efficiency, cooling habits, and home conditions. For the most accurate estimate, use the kWh rate listed on your electric bill.
How to Calculate Your Air Conditioner Running Cost
You can estimate your own AC running cost with a simple formula:
Watts ÷ 1,000 × hours used × electricity rate = cost to run AC
For example, if a 1,000-watt window AC unit runs for 8 hours and your electricity rate is $0.16 per kWh, the cost would be:
1,000 ÷ 1,000 × 8 × $0.16 = $1.28 per day
If you used that unit for 30 days, the estimated monthly cost would be:
$1.28 × 30 = $38.40 per month
For central AC, the math can be less exact because the system cycles on and off throughout the day. But this formula gives you a useful starting point for comparing usage and understanding why your bill may rise during hot weather.
Central AC Cost: What to Expect
A central AC system may use about 3,000 to 5,000 watts while running. Using an example rate of $0.16 per kWh, this could equal about $0.48 to $0.80 per running hour. If the system ran for 8 full hours a day, the monthly cost could be roughly $115 to $192.
Your actual central AC cost depends on several factors, including:
- Outdoor temperature and humidity
- Thermostat setting
- Home size and insulation
- System age and efficiency rating
- Filter and coil cleanliness
- Ductwork condition
- How often does the system cycle on and off
If your central AC runs constantly, cools unevenly, or causes a sudden increase in your energy bill, it may need maintenance, repair, or an efficiency check.
What Affects the Cost to Run AC?
Two homes can have the same air conditioner and still have different cooling costs. That is because AC efficiency depends on the full system and the condition of the home.
System Size and Efficiency
An AC system that is too small may run constantly and still struggle to cool your home. A system that is too large may cycle on and off too often, which can waste energy and leave humidity behind. Proper sizing is important for comfort, efficiency, and long-term performance.
Efficiency also matters. Newer air conditioners often use less electricity than older systems. If your AC is aging, inefficient, or expensive to repair, replacement may help lower operating costs over time.
Thermostat Settings
The lower you set your thermostat, the harder your AC has to work. Even a small adjustment can affect your energy use. A programmable or smart thermostat can help by adjusting the temperature when you are away, asleep, or not using certain areas of the home.
Maintenance and Airflow
Dirty filters, clogged coils, low refrigerant, and worn parts can all make your AC work harder than it should. Poor airflow can also lead to uneven cooling and longer run times. Routine maintenance helps your system run more efficiently and may reduce the chance of unexpected repairs.
Insulation, Air Leaks, and Ductwork
If cooled air escapes through leaky windows, doors, attics, or ductwork, your AC has to run longer to maintain the same temperature. Sealing air leaks, improving insulation, and checking ductwork can help reduce energy waste and improve comfort.
How to Lower Your AC Bill
If your summer energy bills are higher than expected, there are several ways to reduce cooling costs without giving up comfort. Some changes are simple habits. Others may require professional maintenance or system upgrades.
Use Smarter Thermostat Settings
Start by setting your thermostat as high as you can while still staying comfortable. Raising the temperature a few degrees when you are away can reduce runtime and help lower your AC bill.
If you have a programmable or smart thermostat, set a schedule instead of changing the temperature manually throughout the day. This helps prevent your system from cooling an empty home more than needed.
Replace or Clean Your Air Filter
A dirty air filter restricts airflow and makes your AC work harder. It can also affect indoor air quality and comfort. Check your filter regularly during the cooling season, especially if you have pets, allergies, or heavy system use.
Many homes need a filter change every one to three months, but the right timing depends on your system, filter type, and household conditions.
Schedule AC Maintenance
Professional AC maintenance can help your system run more efficiently. During a tune-up, a technician can inspect key components, clean parts of the system, check refrigerant levels, test electrical connections, and look for problems that could affect performance.
Maintenance is one of the best ways to reduce energy waste and help prevent small issues from turning into expensive repairs.
Keep Space Around the Outdoor AC Unit
The outdoor unit works best when air can move freely around it. Remove leaves, weeds, grass clippings, and other buildup near the equipment so your AC does not have to work harder than necessary.
Use Fans and Window Coverings
Ceiling fans can help you feel cooler, which may allow you to raise the thermostat a few degrees. Just remember to turn fans off when you leave the room because fans cool people, not empty spaces.
Closing blinds, curtains, or shades during the hottest part of the day can also help. This is especially useful in rooms with large windows or strong afternoon sun.
Seal Air Leaks and Check Ductwork
Warm outdoor air can enter through gaps around windows, doors, attics, and other openings. Sealing leaks helps keep cooled air inside and reduces how long your AC needs to run.
Ductwork can also affect your AC costs. Leaky or poorly insulated ducts may waste cooled air before it reaches your rooms. If some rooms are too warm while others are too cold, ductwork may be part of the problem.
Limit Heat-Producing Activities During Peak Heat
Ovens, dryers, and other appliances can add heat to your home. When possible, use them in the morning or evening during hot weather. Small habits like this can reduce the cooling load on your AC.
Consider Replacement if Repairs Keep Adding Up
If your AC is older, breaking down often, or struggling to cool your home, another repair may not be the most cost-effective choice. A new high-efficiency system can reduce energy use, improve comfort, and provide more reliable cooling.
Get Help Reducing Your AC Costs
Online estimates and formulas can help you understand the possible cost to run AC, but every home is different. Your cooling costs depend on your equipment, electricity rate, home layout, insulation, ductwork, and comfort preferences.
At Deljo Heating, Cooling & Plumbing, we can inspect your cooling system, review efficiency concerns, recommend cost-saving improvements, and help you decide whether maintenance, repair, or replacement makes the most sense. Our team has helped Chicago homeowners stay comfortable since 1922, and we are ready to help you find a smarter way to cool your home.
Call Deljo at 773-829-4295 or schedule your service online to get started.
Common Questions About AC Costs
Why is my AC bill so high?
Your AC bill may be high because of extreme outdoor temperatures, a low thermostat setting, dirty filters, poor maintenance, leaky ductwork, air leaks, poor insulation, or aging equipment. A sudden increase may also point to a mechanical issue, especially if your system is running longer than usual or not cooling well.
Do newer AC units cost less to run?
Often, yes. Newer systems are usually more efficient than older equipment, especially if your current AC is 10 years old or older, needs frequent repairs, or has not been maintained well. Savings depend on your current system, new system efficiency, home size, and usage habits.
Can AC maintenance lower my energy bill?
AC maintenance can help your system run more efficiently by improving airflow, cleaning important components, checking refrigerant levels, and catching issues early. If your system is dirty or struggling, maintenance may help reduce wasted energy and improve comfort.
What is the best way to lower my AC bill?
The best approach is to combine several steps. Use smart thermostat settings, change filters, schedule maintenance, keep the outdoor unit clear, seal air leaks, use ceiling fans, and close blinds during peak sun. If your system is older or inefficient, a professional assessment can help you decide whether repairs, maintenance, or replacement will save more over time.
