AC Running Cost Calculator
Enter your AC size in tons, its SEER and your runtime to get monthly and seasonal cost — the numbers that decide whether a SEER upgrade pays.
Open calculatorLast updated: 2026-09-15
How the calculation works
- Tons convert to BTU/h (×12,000) and divide by SEER to get average watts drawn at rating conditions.
- Multiply by daily runtime and days for monthly kWh, then by rate for cost.
- The seasonal figure (6 months) supports upgrade payback comparisons.
Worked example
Interpreting the result
The SEER-to-dollars link shows when efficiency upgrades pay: hot climates with long seasons and high rates make 18+ SEER worthwhile; mild climates rarely justify beyond 16. Runtime matters more than SEER in the equation — shading windows and raising the setpoint 2 °F saves more than a SEER point.
Assumptions
- Rating-point average draw; real draw varies with outdoor temperature and cycling.
- Steady electricity rate.
Limitations
- SEER is a seasonal average — actual efficiency at 100 °F is lower (EER).
- Duct losses (often 20–30%) are not included — they multiply everything.
The input that moves the result most: your actual kWh price
Every cost result scales linearly with the rate you enter, and rates vary more between utilities than equipment efficiency varies between models. Taking the price from a recent bill — not a national average — is the difference between a useful estimate and a decorative number. Time-of-use tariffs add a second layer: running the AC during peak windows can cost 2–3× the off-peak rate, which is why pre-cooling before peak hours is a real strategy where those tariffs exist.
SEER is an average, not a promise
- SEER is measured over a whole cooling season, so a 16 SEER unit at milder part-load conditions can beat its rating while a 14 SEER unit in brutal conditions may match it.
- Replacing a 10 SEER unit with 16 SEER cuts cooling energy roughly 35–40% — but only if the new unit is correctly sized; oversizing erases much of the gain through cycling losses.
- Compare units at the same rating standard (SEER vs SEER2 differ by test procedure since 2023) — cross-standard comparisons overstate differences.
Frequently asked questions
How much does it cost to run AC per hour?
A 3-ton 16-SEER unit draws about 2.25 kW → $0.34/hour at $0.15/kWh. Older 10-SEER units of the same size: $0.54/hour.
Is a higher SEER worth it?
Multiply the kWh difference by your rate and runtime. In hot climates with $0.20+/kWh, yes; in mild climates the 14–16 SEER range is usually the economic ceiling.