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.
Last 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.
Formula
kW = tons × 12 / SEER Cost = kW × hours × days × rate
| Symbol | Meaning | Unit |
|---|---|---|
kW | Average electrical draw | kW |
SEER | Seasonal efficiency | BTU/h per W |
rate | Electricity price | $/kWh |
Worked example
A 3-ton, 14-SEER unit running 8 h/day: 3 × 12/14 = 2.57 kW → 617 kWh/month → $92/month at $0.15. The same comfort on an 18-SEER unit: 2.0 kW → $72/month. A $20/month difference over a 6-month season is $120/year — a marginal upgrade unless prices or runtime are higher.
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.
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.