To convert SEER2 to old SEER, multiply by 1.047. To convert SEER to SEER2, divide by 1.047. For example, 15.2 SEER2 equals approximately 15.9 SEER, and 16 SEER equals approximately 15.3 SEER2. The conversion isn't perfectly uniform across all equipment types — variable-speed systems may see a smaller gap — but 1.047 is the accepted industry approximation.
This page provides a comprehensive conversion chart, step-by-step examples, and conversions for all updated metrics (EER/EER2 and HSPF/HSPF2).
SEER2 to SEER Conversion Chart
Key minimums in both standards:
- North AC minimum: 13.4 SEER2 = 14.0 SEER
- South AC minimum: 14.3 SEER2 = 15.0 SEER
- ENERGY STAR AC: 15.2 SEER2 = 15.9 SEER
- Tax credit AC: 17.5 SEER2 = 18.3 SEER
Conversion Formulas
SEER / SEER2
SEER2 to SEER: SEER = SEER2 x 1.047
SEER to SEER2: SEER2 = SEER / 1.047
EER / EER2
EER2 to EER: EER = EER2 x 1.047
EER to EER2: EER2 = EER / 1.047
HSPF / HSPF2
The HSPF conversion is less precise because heating tests involve defrost cycles and strip heat:
HSPF to HSPF2: HSPF2 is approximately HSPF x 0.85 (rough approximation)
HSPF2 to HSPF: HSPF is approximately HSPF2 / 0.85
The HSPF conversion is less reliable than SEER/EER conversions. The heating test involves supplemental electric strips and defrost cycles that interact differently with higher static pressure. The 0.85 factor is a ballpark. For precise HSPF2 values, check the manufacturer's AHRI certificate for the specific model.
EER to EER2 Conversion Chart
HSPF to HSPF2 Conversion Chart (Approximate)
Step-by-Step Conversion Examples
Example 1: Your old AC is rated 16 SEER. What's the SEER2 equivalent?
SEER2 = 16 / 1.047 = 15.3 SEER2
A new 15.3 SEER2 unit is approximately equivalent in efficiency to your old 16 SEER unit.
Example 2: A new AC is rated 18 SEER2. What would it have been rated under the old standard?
SEER = 18 x 1.047 = 18.8 SEER
This unit would have been labeled 18.8 SEER before the 2023 transition.
Example 3: You're comparing your 12 EER window AC to a new 11.5 EER2 model. Which is more efficient?
Convert old EER to EER2: 12 / 1.047 = 11.5 EER2
They're essentially identical in efficiency. The new unit just uses a tougher test standard.
Why the Conversion Isn't Perfectly Uniform
The 1.047 factor is an average. The actual SEER-to-SEER2 ratio varies by equipment type:
PSC (permanent split capacitor) blower motors are the most affected because they can't adjust their speed when resistance increases. ECM (electronically commutated motor) blowers ramp up to maintain airflow, consuming more electricity but with less efficiency degradation.
Practical Guidance for Comparisons
When comparing equipment across standards, always convert to the same scale. If you're shopping for new equipment, everything will be in SEER2. If you're comparing a new purchase to your existing system, convert your old SEER to SEER2 first.
Don't mix metrics in the same comparison. A 15 SEER2 unit is actually slightly more efficient than a 15 SEER unit, even though the numbers match. Converting reveals the truth: 15 SEER2 equals approximately 15.7 SEER.
Key Takeaways
- SEER to SEER2: divide by 1.047. SEER2 to SEER: multiply by 1.047.
- EER to EER2 uses the same 1.047 factor.
- HSPF to HSPF2: multiply by roughly 0.85 (less precise due to heating test complexities).
- 16 SEER = 15.3 SEER2. 15.2 SEER2 = 15.9 SEER. These are the most common conversions.
- Variable-speed systems see a smaller gap (1.03-1.05x) than single-speed with PSC motors (1.05-1.06x).
- Always convert to the same standard before comparing — don't compare SEER numbers to SEER2 numbers directly.
- For exact values, check the manufacturer's AHRI certificate for the specific indoor/outdoor unit combination.
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