Air conditioner electricity cost

Air conditioning is usually the single biggest line on a summer electricity bill — and the one whose cost swings most with the size of the unit and how hard it has to work.

Short answer at the example rate of $0.17/kWh: a typical 3,500 W air conditioner running 8 hours a day, 30 days a month uses about 840 kWh and costs $142.80 a month. Put in your own wattage, schedule and rate below — a large window unit or small mini-split draws around 1,500 W, a typical central system about 3,500 W while the compressor runs, and a big central system 5,000 W or more.

The $0.17/kWh default is a rough example rate — about the US residential average on EIA figures, and it moves over time. Type in the rate from your own electricity bill for numbers that mean anything for your home.

Low, typical and high — side by side

The default schedule is 8 hours of compressor run time a day across a 30-day month — a hot month, not a mild one. All three rows use that same schedule and the $0.17/kWh example rate; only the wattage changes.

What drives the number

Three things: the size of the unit, the gap between the outdoor temperature and your thermostat, and how well the house holds cool air. The wattage on the nameplate is the draw while the compressor runs — a system in a heatwave runs nearly flat out, while the same system in May cycles on and off and averages a fraction of its rating.

That cycling is why two households with identical systems get different bills, and why this page treats hours as "compressor hours", not "hours the thermostat was set to cool". If you have a smart thermostat, its runtime report is the best source for your real daily hours.

Cheaper ways to get the same cool room

Run time is the lever. A ceiling fan (about 75 W) makes a room feel cooler and lets you raise the set point; closing blinds on sun-facing windows cuts the heat the AC has to remove; and on a time-of-use plan, pre-cooling before the peak window moves compressor hours to the cheap rate — the time-of-use calculator on the home page shows what that split is worth.

Questions

How much does it cost to run AC for one hour?

A typical 3,500 W central system uses 3.5 kWh in an hour of compressor run time — about $0.60 at $0.17/kWh. A 1,200 W window unit uses 1.2 kWh, about $0.20 an hour.

Why is my AC bill lower than the estimate?

The compressor cycles. On a mild day it may run only a third of the time the fan does, so effective daily hours land well under the 8 used here. Lower the hours-per-day figure to match, or work from the kWh on a real bill.

Does raising the thermostat setting actually save much?

Each degree warmer generally trims a few percent of cooling energy, because the compressor runs less. The bigger lever is run time: shading, sealing leaks and pre-cooling on off-peak rates (if you have them) all cut the hours the unit spends at full draw.

Is a mini-split cheaper to run than central AC?

Usually, per room cooled — a mini-split serving one room might draw 800–1,500 W instead of a whole-house 3,500 W, and it only cools the room in use. Whole-house comparisons depend on the home and climate.

More appliances: the main calculator and whole-home list · every preset on one chart · how the formula works