What Is SEER2? The Rating, and How It Differs From SEER

What SEER2 means

Here's what SEER2 means in plain language: it's how much cooling a system delivers over a typical cooling season, divided by the electricity it uses to do it. SEER stands for Seasonal Energy Efficiency Ratio. The “2” refers to the current Department of Energy test. It doesn't mean a second season or a second kind of ton.

Lots of people search “what is SEER2” because the labels on the box changed. A contractor might still say SEER out of habit, but a product page should say SEER2 when that's the figure on the current spec sheet. Our older SEER explainer covers the older label, and this page covers the rating on equipment sold today.

SEER2 is a cooling-season number, so it doesn't describe heating. When the spec sheet lists heating efficiency, that's HSPF2. How much heat you'll get in winter is a different question, and our mini split heat pump guide covers it.

How to read a SEER2 rating

A SEER2 rating is a ratio, not a capacity, so it won't tell you how many BTU your room needs. Two systems can have the same BTU rating and different SEER2 numbers. Our 12,000 BTU class is a good example: one model is 19 SEER2 with a full 12,000 BTU/h of cooling, and the other is 17 SEER2 with 11,500 BTU/h of cooling on the spec sheet.

A higher number means the system used less electricity in lab testing for the cooling it delivered. It doesn't mean the room will feel colder, and it doesn't mean the unit is the right size. For capacity, see the BTU to tons guide. For your room, try the Size Finder.

If you'd like a bill estimate based on the ratings on the spec sheet, the Energy Savings calculator compares an inverter mini split with the equipment you have now. It won't turn a SEER2 point into a guaranteed dollar savings, though. Any dollar figure you see in a general US article is a commonly published estimate, not a Classic America price.

What is a good SEER2 rating?

What counts as “good” depends on what the spec sheet actually lists, not on a slogan. In our catalog, the confirmed cooling ratings are 17, 19, 23, and 24. Seventeen is the lower of the two systems in the 12,000 BTU class, and it's a published SEER2, not a guess. Twenty-three on the 9,000 BTU model and 24 on DUET (non-ducted) are the top of our range.

There are federal minimums, and they vary by region and by whether the equipment is a heat pump or cooling-only. We won't reprint every regional cutoff here. The number that matters for any model is the one on its spec sheet. And even a rating well above the minimum can be the wrong machine if the BTU don't match your room.

SEER2 vs SEER

SEER2 vs SEER is a change in the test, not just the name. On January 1, 2023, the US Department of Energy started requiring the updated test (often called Appendix M1) for new central air conditioners and heat pumps. For ducted systems, the lab raises the external static pressure the blower works against, so the rating is closer to a real-world install. Ductless equipment is tested under the updated procedure too.

Since the tests are different, a SEER number and a SEER2 number aren't the same claim. A unit once described as “20 SEER” isn't automatically “20 SEER2.” That's the heart of the question “what is the difference between SEER and SEER2”: same job (seasonal cooling efficiency), different procedure, different number.

SEER2 on this lineup

The 19 SEER2 model covers up to about 550 square feet, not 600. Its product URL still has an older “600-sqft” phrase in it, so go by the spec sheet. And when your room is sunny, tall, or poorly insulated, trust the Size Finder over either number. Our mini split sizing guide walks through those details, and the BTU calculator walkthrough gives you a click-by-click tour of the same tool.

Compare the models next to the bars. The card for the 23,000 BTU system shows **17 SEER2**.

The 9,000 BTU mini split is our 23 SEER2 system, on the 9,000 BTU hub. Both 12,000 BTU-class systems are on the 12,000 BTU hub: the 19 SEER2 12,000 BTU mini split and the 17 SEER2 12,000 BTU mini split. You'll find DUET on the dual-zone hub, and the 23,000 BTU mini split, rated 17 SEER2, on the 23,000 BTU / 2 ton hub. Want to see every spec at once? Line them up in the compare tool.

The rating is not the room. The free Size Finder turns sun, ceiling height, insulation, and climate into a BTU number. The Energy Savings calculator is where a SEER2 figure becomes a bill comparison, not a promised discount.

Window units are rated in CEER, not SEER2

The window air conditioners in our catalog don't carry a SEER2 rating. Both the 8,000 BTU window air conditioner and the 12,000 BTU window air conditioner list CEER 10.9. CEER is the combined energy-efficiency ratio used for window units, so calling it SEER2 would mix up two different tests. Our window AC vs mini split comparison keeps the labels straight, along with the plug-in install and the fact that these window units don't heat.

HSPF2 is the heating rating, not SEER2

If the mini split is a heat pump, its spec sheet may also list HSPF2, the heating-season counterpart, often split into Region IV and Region V. Here's what we publish: 9.0 / 7.76 on the 9,000 BTU model, 7.5 / 7.2 on the 19 SEER2 12,000 BTU model, 9.5 / 8.1 on the 17 SEER2 model, and 10.5 / 9.5 non-ducted on DUET (8.5 / 7.33 on the ducted configuration). The 23,000 BTU model is rated HSPF2 9.5 in Region IV and 8.5 in Region V.

HSPF2 still isn't the BTU you'll get on a cold night, because output drops as the outdoor temperature drops. You'll find that chart in the mini split heat pump guide. The Size Finder checks your heating load against the published heating capacity, rather than assuming the cooling BTU will handle both jobs.

What the rating does not decide

Even a great SEER2 rating on an undersized head will leave the room warm on the hottest afternoon, and an oversized head can short-cycle and feel clammy. If your quote came in tons, start with the BTU to tons guide, then run your room through the Size Finder. These systems come with 5 years on the compressor and 1 year on parts. Planning the mount is great homeowner work, while refrigerant connections, the vacuum, and a dedicated electrical circuit are jobs for a licensed HVAC professional.