SEER / EER / COP Converter
Enter a SEER rating to see the equivalent EER, COP, kW per ton and tons per kW — with an explanation of what each rating actually measures.
Last updated: 2026-09-15
How the calculation works
- SEER averages efficiency over a seasonal temperature range; EER is a single rating point at 95 °F outdoors.
- The DOE-style approximation EER ≈ SEER × 0.875 converts between them.
- COP is the dimensionless ratio (EER / 3.412), and kW/ton is the traditional HVAC industry metric (12 / SEER).
Formula
EER ≈ SEER × 0.875 COP = EER / 3.412 kW/ton = 12 / SEER
| Symbol | Meaning | Unit |
|---|---|---|
SEER | Seasonal Energy Efficiency Ratio | BTU/h per W |
EER | Energy Efficiency Ratio (95 °F rating point) | BTU/h per W |
COP | Coefficient of Performance | W/W |
Worked example
Interpreting the result
Higher SEER means less electricity per BTU of cooling, but the savings diminish: going from 14 to 16 SEER saves ~12%, from 16 to 18 another ~11%. Whether the premium pays back depends on run hours and electricity price. COP is the universal metric — heat pumps and chillers worldwide are compared with it.
Assumptions
- The 0.875 SEER→EER factor is a rule of thumb; actual EER depends on the specific unit.
- Ratings apply at standard test conditions, not necessarily your climate.
Limitations
- Does not apply to gas furnaces (AFUE) or geothermal ratings (COP at different conditions).
- Real-world savings depend on climate, duct losses and thermostat habits.
Frequently asked questions
What SEER should I buy?
In hot climates with long cooling seasons, 16–18 SEER usually pays back; in mild climates the jump from 14 to 16 is often the sweet spot. Compare the electricity savings against the price difference for your run hours.
Is COP the same as efficiency?
For heat pumps, COP above 1 means more heat moved than electricity consumed — possible because the unit moves existing heat rather than creating it. Resistance heat is COP 1.0.