Air Conditioner Running Cost Calculator

Every cost estimate starts by turning cooling capacity into electrical draw. The EER on a unit’s label is its cooling output in BTU per hour divided by its power input in watts, so the full-load draw is simply BTU/hr ÷ EER. A 12,000 BTU unit rated EER 11 pulls about 1,091 watts when the compressor is running flat out.

Central systems and mini-splits are not labelled in EER. They carry a SEER (or SEER2) rating, a seasonal average measured across a range of outdoor temperatures rather than a single full-load point. DOE FEMP’s own tables work a season’s energy as the capacity times the hours over that seasonal ratio, cell by cell: a 36,000 BTU/hr unit at SEER2 15.2 running 3,409 hours a year uses 8,074 kWh. This tool does the same for both kinds of rating. NREL’s Building America benchmark gives an approximate conversion from SEER to EER (EER = -0.02 × SEER² + 1.12 × SEER); the tool uses it only for the rating-point draw tile, and only below SEER 28, where that curve turns.

Watts alone do not set the bill. A compressor rarely runs continuously; it cycles on and off to hold the thermostat setpoint. The fraction of time it actually runs is the duty cycle, and it is the largest single source of real-world variation. Multiply the average draw by the hours the unit is on, divide by 1,000 for kilowatt-hours, then multiply by your rate; a month here is a year of days over twelve months. For the raw watts-to-kWh step on any load, the kWh calculator shows the same arithmetic.

The table below runs the six units with a printed rating behind the presets through the same usage: 8 hours a day, a 70% duty cycle, and the default rate of 17.23 cents per kWh, EIA’s 2025 U.S. residential average. The hours and duty are this page’s defaults, not a measurement of any home: replace them with your own. Avg draw is the capacity over the printed ratio, times the duty cycle; monthly cost is a year of days at that draw over twelve months.

*At 17.23 cents per kWh, 8 hours a day and a 70% duty cycle. Enter your own figures for your own result. Two patterns stand out. On DOE FEMP’s three central rows, the SEER2 23.5 unit costs $44.96 a month against $78.85 at SEER2 13.4, because the energy is the capacity over the seasonal ratio. And size sets the bill: at the same rating, hours and duty, a 5-ton (60,000 BTU) system costs five times what a 1-ton (12,000 BTU) unit costs, since its draw is the capacity over the ratio.

1. Raise the setpoint a few degrees. Each degree higher cuts run time and the compressor cycles less, dropping duty cycle.
2. Right-size the unit. An oversized AC short-cycles and an undersized one runs near 100% duty in heat, and both cost more than a correctly matched unit. Match BTU to the room, not to the biggest box on the shelf.
3. Replace a low-SEER central system. Swapping a SEER 14 unit for a SEER 20 mini-split cuts the per-BTU running cost by 30%, since the energy is the capacity over the seasonal ratio. Use the electricity bill estimator to see the whole-home impact across every category.
4. Offset cooling with solar. AC load peaks in the afternoon, exactly when rooftop panels produce most. The solar ROI calculator shows the payback period when summer cooling is the load you are sizing for.