SEER to EER Converter
Turn an air conditioner or heat pump rating into every other efficiency metric: SEER, SEER2, EER, EER2 and COP. Add a second unit to see what the efficiency difference is worth on your electric bill each year.
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From the yellow EnergyGuide label or AHRI certificate.
e.g. your old unit or a cheaper quote.
Roughly 600–900 in cool northern climates, 1,000–1,500 in mixed climates and 2,000–3,000 in hot southern ones.
US residential average was about $0.17/kWh in 2025 (EIA); use the rate on your bill.
How to use the SEER to EER Converter
- Pick the rating you know: SEER, SEER2, EER, EER2 or COP, and type the number from the EnergyGuide label.
- Choose ducted or ductless so the SEER2 and EER2 factors match your system.
- Read the converted ratings, the main result shows the matching EER or SEER.
- Optionally compare a second unit: enter its rating, the capacity, your cooling hours and electricity price.
- Check the yearly and lifetime savings, then download the reference table if you need it.
SEER, SEER2, EER, EER2 and COP formulas
| Conversion | Formula | Example |
|---|---|---|
| SEER → EER | EER ≈ −0.02 × SEER² + 1.12 × SEER | SEER 16 → EER 12.8 |
| EER → SEER | SEER ≈ (1.12 − √(1.2544 − 0.08 × EER)) ÷ 0.04 | EER 12 → SEER 14.4 |
| SEER → SEER2 (ducted) | SEER2 ≈ SEER × 0.955 | SEER 15 → SEER2 14.3 |
| EER → EER2 (ducted) | EER2 ≈ EER × 0.96 | EER 12.2 → EER2 11.7 |
| EER → COP | COP = EER ÷ 3.412 | EER 12 → COP 3.52 |
| Full-load power | kW per ton = 12 ÷ EER | EER 12 → 1.0 kW/ton |
| Yearly energy | kWh = BTU/h × hours ÷ (SEER × 1000) | 36,000 × 1,200 ÷ 16,000 = 2,700 kWh |
The SEER–EER relationship is a statistical fit published by NREL (Wassmer & Brandemuehl) for typical single-speed equipment. It peaks near SEER 28, so it is not meant for high-end inverter units. Two units with the same SEER can have quite different EERs; when peak summer performance matters, read the EER from the AHRI certificate.
Which rating should you compare?
- SEER / SEER2: best for estimating the yearly energy bill, because it averages performance over a cooling season.
- EER / EER2: best for hot, dry climates and for sizing peak electrical load, because it is measured at 95 °F outdoors. Some southwestern states also set minimum EER2 values.
- COP: the physics view (watts of heat moved per watt used). It is common for heat pumps, chillers and equipment rated outside the US.
- HSPF / HSPF2: the heating-season rating of a heat pump. It is a different test and cannot be converted from SEER.
Never mix old and new ratings when comparing quotes: a SEER2 15.2 unit is roughly equal to a SEER 16 unit, not worse than it. Choose the same rating type for unit A and unit B in the calculator so the comparison is fair.
US minimum efficiency since 2023
| Region | Split AC (< 45,000 BTU/h) | Split heat pump |
|---|---|---|
| North | 13.4 SEER2 (≈ 14 SEER) | 14.3 SEER2, 7.5 HSPF2 |
| Southeast | 14.3 SEER2 (≈ 15 SEER) | 14.3 SEER2, 7.5 HSPF2 |
| Southwest | 14.3 SEER2 plus 11.7 EER2 (≈ 12.2 EER) | 14.3 SEER2, 7.5 HSPF2 |
Figures reflect the US Department of Energy standards that took effect on January 1, 2023. Larger units and packaged systems have slightly different minimums; check the current DOE rules for your equipment.
Frequently asked questions
How do you convert SEER to EER?
A widely used approximation (Wassmer and Brandemuehl, NREL) is EER ≈ −0.02 × SEER² + 1.12 × SEER. A SEER 16 unit works out to about EER 12.8, and SEER 14 to about EER 11.8. It is an estimate for typical single-speed systems; the AHRI certificate lists the real tested EER.
What is the difference between SEER and EER?
EER is efficiency at one hot test point (95 °F outdoors, 80 °F indoors at 50% humidity). SEER is a seasonal average over a range of milder outdoor temperatures, so it is always higher than EER for the same unit. EER tells you how the unit performs on the hottest days.
How do I convert SEER to SEER2?
Since January 2023, ratings use the M1 test procedure with higher external static pressure. For ducted central systems SEER2 is about 4.5% lower: SEER2 ≈ SEER × 0.955, so SEER 14 ≈ SEER2 13.4 and SEER 15 ≈ SEER2 14.3. Ductless mini-splits change very little.
What is a good SEER rating?
Since 2023 the US federal minimum for new central air conditioners is 13.4 SEER2 (14 SEER) in the North and 14.3 SEER2 (15 SEER) in the South and Southwest. 16 to 18 SEER is a common high-efficiency choice, and variable-speed inverter systems and mini-splits can exceed 20.
How do you convert EER to COP?
Divide EER by 3.412, because one watt equals 3.412 Btu per hour. EER 12 is a COP of 3.52, meaning the unit moves about 3.5 watts of heat for every watt of electricity it uses.
How much does a higher SEER save?
Cooling energy is proportional to 1 ÷ SEER. Going from SEER 10 to SEER 16 cuts cooling electricity by 37.5%, but going from 16 to 20 cuts it by another 20% of a smaller number. The calculator uses kWh = BTU/h × hours ÷ (SEER × 1000) so you can see the dollar difference for your climate and rate.
How many cooling hours should I use?
Use full-load equivalent hours: the yearly cooling energy divided by the unit's capacity. As a rough guide, cool northern climates see 600 to 900 hours, mixed climates 1,000 to 1,500 and hot southern climates 2,000 to 3,000 hours.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.