Cost to Run an Air Conditioner
A window AC (10,000 BTU, ~1,200W) costs about $0.19/hour or $45-80/month running 8-12 hours daily. Central AC costs $100-200/month in summer depending on home size, efficiency, and climate. Calculate your cost with the Power Cost Calculator.
Key Takeaways
- Window units typically draw 500-1,500 watts depending on BTU rating.
- Each degree lower on the thermostat increases costs about 3%.
- Ceiling fans allow raising thermostat 4°F without losing comfort.
Explanation
Window units typically draw 500-1,500 watts depending on BTU rating. A common 10,000 BTU unit uses about 1,200 watts. Portable ACs use more power than window units for the same cooling capacity.
Central AC systems range from 2,000-5,000 watts. A 3-ton system (36,000 BTU) might draw 3,500 watts while running. However, central AC cycles on and off based on thermostat settings, not running continuously.
Efficiency ratings matter greatly. A high-SEER central system or Energy Star window unit can cut cooling costs by 20-40% compared to older or less efficient models.
SEER (Seasonal Energy Efficiency Ratio) directly determines your operating cost. A 14-SEER system costs roughly 30% more to run than a 20-SEER system for the same cooling output. Since 2023, the federal minimum SEER rating for new residential AC units is 14 in northern states and 15 in southern states. Upgrading from a 10-SEER system to a 16-SEER unit can save $400-700 per year in hot climates.
Proper AC sizing is critical for both efficiency and comfort. An oversized unit cools the air quickly but cycles off before removing enough humidity, leaving the home feeling clammy. An undersized unit runs constantly without reaching the set temperature. A Manual J load calculation performed by an HVAC technician determines the correct tonnage for your home's square footage, insulation, and window area.
Mini-split ductless systems avoid the 20-30% energy loss that occurs in leaky ductwork. A typical home loses a significant portion of cooled air through duct joints, gaps, and uninsulated runs through hot attics. Mini-splits deliver cooled air directly to each room and allow zone-based temperature control, so unoccupied rooms are not cooled unnecessarily.
Pre-cooling your home during off-peak electricity hours can reduce costs if you have time-of-use pricing. Running the AC aggressively in the early morning when rates are low, then raising the thermostat during expensive afternoon peak hours, takes advantage of the home's thermal mass. Well-insulated homes can coast for 2-3 hours with the thermostat raised before indoor temperatures become uncomfortable.
Things to Know
- Each degree lower on the thermostat increases costs about 3%.
- Ceiling fans allow raising thermostat 4°F without losing comfort.
- Heat pumps cost about half as much to run as standard central AC for cooling.