SEER and SEER2
Seasonal energy efficiency ratio, the cooling output over a season divided by the electricity used. SEER2 is the current United States test procedure, measured under higher external static pressure, so SEER2 figures read lower than older SEER values for the same equipment.
Also called SEER, SEER2
What is SEER2?
SEER is seasonal cooling output divided by the electricity used to produce it. SEER2 is the current United States test, run at a higher external static pressure, so its numbers read lower than SEER.
SEER and SEER2: how it works
The test runs equipment across a set of conditions meant to represent a cooling season and divides the total cooling delivered by the total electricity used. SEER2 keeps the idea and changes the conditions, the main change being that ducted equipment is tested against a realistic duct resistance instead of a nearly free-blowing one, which is why the same machine scores lower under the new procedure.
Where you meet the term
- On a North American equipment label and in the AHRI certified ratings directory.
- In a minimum efficiency requirement, where regional standards set a floor for what may be installed.
- In a rebate or incentive programme, where a SEER2 threshold decides eligibility.
How to check it
- Check whether the figure is SEER or SEER2. Marketing material sometimes still quotes the older number. The two are not interchangeable and comparing them directly overstates the older equipment. Owner check
- Look the pairing up in the certified directory. Ratings belong to a matched indoor and outdoor combination. The AHRI directory lists the certified figure for the specific pairing. Owner check
Figures you will see
| Condition | Figure | What it tells you |
|---|---|---|
| What SEER2 changed | 0.5 in. w.c. external static | Ducted equipment is tested against realistic duct resistance rather than 0.1 in. w.c. |
| Effect on the number | SEER2 reads lower than SEER | For the same equipment, because the test is harder |
| European counterpart | SEER under ecodesign | Also a seasonal ratio, but a different test and climate profile, so not interchangeable |
SEER and SEER2: what it is not
- SEER2 and SEER are not the same scale. A SEER2 number placed beside an older SEER number makes the older equipment look better than it is.
- The rating belongs to a matched pair. An outdoor unit installed with a different indoor coil does not carry the certified figure.
- A seasonal rating is not what the system achieves in your house. It is a comparison figure produced under a defined procedure.
SEER and SEER2 questions
Why is my new system's SEER2 lower than my old system's SEER?
Because the test changed rather than the equipment getting worse. SEER2 tests ducted systems against a much higher external static pressure, which reflects real duct systems and produces a lower number for the same machine.
What is a good SEER2 rating?
Regional minimums set the floor and higher ratings cost more to buy. Whether the extra is worth it depends on cooling hours and electricity price, so the comparison is between certified figures for equipment you would actually install.
Can I compare a US SEER2 figure with a European SEER figure?
No. Both are seasonal ratios but they use different test conditions and climate profiles, so the numbers are not on the same scale.
Where this definition comes from
Written from standards body publication, government guidance material held in the HVAC Bench evidence record. Where a document limits a definition to certain models, that limit is repeated here rather than generalised across a brand.
- AHRI Directory of Certified Product PerformanceCertified SEER2, EER2, and HSPF2 ratings for matched North American equipment combinations.
- Energy label and ecodesignThe European framework behind SCOP, seasonal space heating efficiency, and the product energy label.