What is SEER2?
SEER2 is the current efficiency rating for central air conditioners and heat pumps in cooling mode. Higher is better, but the number is only part of the story.
SEER2 is the Seasonal Energy Efficiency Ratio under the updated federal test method. It rates how efficiently a central air conditioner or heat pump cools over a whole season. A higher number means less electricity used for the same cooling.
It replaced the older SEER label on new equipment. If you are comparing quotes, you will now see SEER2 on the paperwork.
Why the test changed
The old SEER test measured equipment under easy lab conditions with almost no resistance to airflow. Real ducts push back. SEER2 adds more realistic airflow resistance, so the same unit gets a slightly lower number than it did before.
That means a SEER2 value and an older SEER value are not directly comparable. A unit does not get worse when the label changes. The ruler changed.
What the number tells you
SEER2 is cooling output over the season divided by the electricity used. It is useful for one job: comparing two units of the same type tested the same way.
What the number leaves out
- Whether the unit is the right size for your house
- How leaky your ducts are
- How well the installation was done
- Your local climate and how many hours you really run cooling
A high rated unit that is oversized or installed on poor ducts will disappoint. The rating assumes a good install.
SEER2, HSPF2 and EER2
| Rating | What it covers |
|---|---|
| SEER2 | Seasonal cooling efficiency |
| EER2 | Cooling efficiency at a single hot condition |
| HSPF2 | Seasonal heating efficiency of a heat pump |
If you live somewhere very hot, EER2 can matter as much as SEER2. If you are buying a heat pump, check HSPF2 too.
Minimums depend on where you live
Federal minimum efficiency levels vary by region and equipment type, and they change over time. Check the current requirement for your area with your contractor or the Department of Energy rather than relying on an old article.
Our advice
Do not pay extra for the last few points of SEER2 before you have fixed sizing and ducts. A well sized, well installed mid range unit usually beats a top rated unit installed badly. Compare ENERGY STAR listings, and ask your contractor to explain what the rating means for your climate.
Frequently asked questions
What is the difference between SEER and SEER2?
SEER2 uses a newer test with more realistic airflow resistance. The same unit scores a little lower under SEER2, so the two numbers cannot be compared directly.
Is a higher SEER2 always better?
A higher number means more efficient cooling, but sizing, duct condition and installation quality affect real results as much as the rating.
Do I need SEER2 for a heat pump?
Yes for cooling mode. For heating, look at HSPF2 as well.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- ENERGY STAR. Energy Savings at Home: Heating & Cooling
- US EPA. Section 608 of the Clean Air Act