EER to SEER2 Conversion
Convert a single-point EER rating into an approximate seasonal SEER2 value — a documented approximation for quickly comparing spec sheets that quote different metrics.
Calculator
EER 12.0 is roughly SEER 13.33 — a documented approximation (EER is a single-point full-load metric; SEER is seasonal).
EER (Energy Efficiency Ratio) is a single-point rating measured at one hot outdoor condition (95°F), while SEER2 is a seasonal average across a range of temperatures. They are not the same thing, but a widely used rule of thumb lets you translate between them for a quick comparison when one product lists EER and another lists SEER2.
This converter applies that documented approximation and shows the arithmetic, so you can sanity-check a window-unit EER against a central-system SEER2 without pretending the two metrics are identical.
Formula
The documented approximation used here:
SEER2 ≈ EER ÷ 0.9
Equivalently, EER ≈ SEER2 × 0.9. The 0.9 factor is an industry approximation, not an exact identity — a seasonal average is always higher than a single hot-day point value because the equipment runs more efficiently at milder temperatures.
Approximation only. EER is a fixed-condition (95°F) metric; SEER2 is the DOE 2023 seasonal test. For an exact figure, read both numbers off the equipment’s EnergyGuide label rather than converting.
Worked example
Convert an EER of 12:
- SEER2 ≈ 12 ÷ 0.9 = 13.33
So a window unit rated EER 12 is roughly comparable to a central system around SEER2 13.3 — useful for a ballpark, but treat it as an estimate, not a spec.
Why EER and SEER2 are not the same
Why the two metrics differ: EER is captured at a single 95°F outdoor test point and full load, which is close to the worst case. SEER2 averages performance across a season that includes many milder hours, when the same equipment runs more efficiently — so the seasonal number is always higher. The 0.9 divisor is a convenient middle-ground approximation; the true relationship varies by equipment design (single-stage vs. variable-speed) and climate.
Use this only to compare like-for-like intent, for example a portable or window AC (usually rated in EER) against a central split system (rated in SEER2). For efficiency savings and payback, work from the actual ratings on the label and feed them into the SEER2 savings tool.
Reference table
| EER | Approx. SEER2 (EER ÷ 0.90) |
|---|---|
| 8 | 8.89 |
| 9 | 10.00 |
| 10 | 11.11 |
| 11 | 12.22 |
| 12 | 13.33 |
| 13 | 14.44 |
| 14 | 15.56 |
Documented approximation (SEER ≈ EER ÷ 0.9); read exact ratings off the EnergyGuide label.