SEER2 to SEER Conversion: Calculator + Equivalency Chart

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

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

EER to EER2 Conversion Chart

HSPF to HSPF2 Conversion Chart (Approximate)

Step-by-Step Conversion Examples

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.

The Physics Behind the 1.047 Factor

The 1.047 SEER-to-SEER2 approximation exists because the DOE test procedure changed on January 1, 2023 — the physical unit did not. What changed is the external static pressure the equipment must overcome during the efficiency test.

Under the old SEER test, the indoor blower was tested at 0.1 in. w.c. of external static pressure — a very low resistance that no realistic residential duct system produces. Under the new SEER2 test (DOE 10 CFR Part 430 Subpart B Appendix M1), external static pressure was raised to 0.5 in. w.c. — much closer to the resistance typical ducted systems actually present.

At higher static pressure, the blower motor draws more power to move the same air volume. The extra motor draw is real; the equipment's cooling capacity isn't reduced, but the ratio of BTU-per-watt-hour drops. That drop shows up as a lower SEER2 number for the same unit.

The 4.7% average reduction is DOE's estimate for typical residential central AC and heat pumps across the equipment class. Individual units may shift more or less depending on their blower motor characteristics — a variable-speed ECM blower handles the higher static pressure more gracefully than a fixed-speed PSC motor, so a variable-speed unit's SEER-to-SEER2 ratio may be closer to 1:1, while a fixed-speed PSC unit's may exceed the 1.047 average.

When to Use Each Conversion Direction

SEER → SEER2 (existing unit rated in old scale, need current-code equivalent):

• Repair-vs-replace decisions on 2015–2022 equipment where the nameplate shows SEER but the local code minimum is now written in SEER2
• Rebate-program eligibility checks where the program threshold is written in SEER2 but you have old paperwork
• Comparing your existing system to what current-code new equipment would deliver

SEER2 → SEER (new-equipment quote in SEER2, need to compare against older stored data):

• Comparing 2026 new-install pricing against 2020s repair-cost records where the reference SEER was in the old scale
• Historical energy-savings estimation where your baseline utility data uses SEER
• Interpreting older technical documents that list target efficiencies in SEER

The AHRI-Certified Rating Is Authoritative

The 1.047 factor is a rule-of-thumb approximation, not an exact conversion. For any specific model that matters (a warranty claim, a code-compliance letter, a rebate application), look up the actual AHRI-certified rating in both scales on the AHRI Directory (ahridirectory.org). Many manufacturers publish both SEER and SEER2 for units certified during the 2023 transition period; for units certified before the transition, only SEER is available and the 1.047 approximation is the best you can do.

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

Frequently Asked Questions

Is 15.2 SEER2 the same as 15.2 SEER?

No. 15.2 SEER2 is actually more efficient than 15.2 SEER. Converting to the same standard: 15.2 SEER2 equals about 15.9 SEER. The SEER2 test is harder, so the same number represents better real-world performance.

Do I need to convert if I'm only comparing new equipment?

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