An air conditioner’s running cost is its electrical draw times the hours it runs times your rate — and the draw comes from the cooling capacity divided by the unit’s efficiency. Once you know the input power, the arithmetic is the same as any other appliance.
How it’s worked out
Electrical input = cooling capacity ÷ efficiency (EER/COP), so a 12,000 BTU (1 ton, 3.5 kW) unit at an EER of 3.5 draws about 1 kW. Scale that by the average compressor load, multiply by hours for the kWh, and by your rate. So 1 kW at 75% load for 6 hours is 4.5 kWh a day — at $0.25/kWh, about $1.13 a day or $34 a month.
How much power does it use?
As a rule of thumb, a modern split draws about 1 kW per ton (12,000 BTU) of cooling: roughly 700–1,100 W for a 12,000 BTU (1 ton) unit and 1,500–2,200 W for a 24,000 BTU (2 ton) unit at full output. The real average is lower, because the compressor rarely runs flat out for a whole session.
Aircon Running Cost Calculator
Enter unit size, efficiency, hours and your rate for the cost per hour, day and month.
What is EER or COP?
Both are efficiency ratios: cooling (EER) or heating (COP) output divided by electrical input. An EER of 3.5 means 3.5 kW of cooling for every 1 kW of electricity. Find it on the unit’s energy label or datasheet — modern inverter units are typically 3 to 4, and the higher the number, the cheaper it is to run.
Does heating cost the same?
Roughly, yes — a reverse-cycle unit heats with about the same efficiency (COP) as it cools, so you can use the same calculation with the heating capacity. That also makes it about a third of the cost of a plug-in resistance heater, which delivers just 1 kW of heat per kW of electricity.
Cutting the running cost
Set the thermostat moderately — each degree of extra cooling adds roughly 5–10% to consumption. Keep filters clean and the outdoor unit shaded and unobstructed, seal the room, and size the unit correctly: an undersized unit runs flat out all day, while a well-sized inverter unit throttles back once the room is at temperature.