SEER vs SEER2: What the New Efficiency Standard Means for Your AC

If you have shopped for an air conditioner recently, you have probably seen efficiency listed as SEER2 rather than SEER and wondered what changed. The short answer: the testing standard was updated, the numbers shifted slightly, and the minimums you are allowed to buy now depend on where you live. Here is what SEER vs SEER2 actually means for your next system and your energy bill.

What SEER measures

SEER stands for Seasonal Energy Efficiency Ratio. It describes how much cooling a system delivers over a season for each unit of electricity it uses. A higher SEER number means a more efficient system that costs less to run. The concept has not changed; the way it is tested has.

Why SEER2 replaced SEER in 2023

As of January 1, 2023, the U.S. Department of Energy moved to a new test procedure that measures equipment under higher external static pressure, which better reflects the real-world ductwork a system has to push air through. The result of this tougher test is SEER2. Because the test is more demanding, a unit’s SEER2 rating is roughly 4 to 5 percent lower than its old SEER number, even though the physical equipment performs the same. In other words, a 15 SEER unit is about 14.3 SEER2. You can read the background on the Department of Energy’s cooling pages.

New minimum efficiency by region

The 2023 change also raised and split the minimum efficiency you are allowed to install by region. In northern states the minimum for a split-system air conditioner is 13.4 SEER2, while in southern and southwestern states it is 14.3 SEER2 for smaller systems. That regional split exists because cooling matters more in hot climates, so those regions require more efficient equipment.

What SEER2 should you buy?

Higher SEER2 costs more up front but lowers your monthly bill. Whether the upgrade pays back depends on how hot your climate is, how many hours the system runs, and your local electricity rate. In hot states with high electricity prices, moving from a base 14.3 SEER2 to 16 or 18 can pay for itself over the life of the system. In mild climates the savings are smaller. Run the numbers for your situation with our SEER2 savings calculator, and see what a given unit costs to run each month with the cooling cost calculator.

The takeaway

SEER2 is not a new kind of efficiency, just a more realistic way of measuring it. Expect the numbers on new equipment to look slightly lower than the old SEER ratings, check the minimum required in your region, and let your climate and electricity rate decide how high to go. When you are ready to price a system, estimate the installed cost with our AC replacement cost calculator.

SEER2’s cousins: EER2 and HSPF2

SEER2 did not change alone. The same 2023 update introduced EER2, which measures cooling efficiency at a single high-temperature design point rather than across a season, and HSPF2, which rates a heat pump’s heating efficiency. If you are shopping for a heat pump rather than a straight air conditioner, HSPF2 is the number that tells you how efficiently it heats, and it matters most in colder climates where the unit runs hard all winter. As with SEER2, the new heating and single-point ratings read slightly lower than the old SEER, EER, and HSPF figures because the test is tougher, not because the equipment got worse.

How to read a modern efficiency label

When you compare two systems, make sure you are comparing SEER2 to SEER2, not an old SEER number against a new SEER2 one, or the more efficient unit will look worse than it is. Ask the contractor for the AHRI certificate for the exact indoor and outdoor combination being installed, since a rating applies to the matched pair, not just the outdoor condenser. A mismatched coil can leave you paying for efficiency you never actually receive. For heat pump shoppers, weigh both the SEER2 cooling number and the HSPF2 heating number, then price the unit with our heat pump cost calculator.

Frequently asked questions

Is SEER2 better than SEER?

SEER2 is not better or worse; it is a more realistic test. A unit’s SEER2 rating is about 4 to 5 percent lower than its old SEER rating for the same equipment.

What is the minimum SEER2 in 2026?

It depends on region: about 13.4 SEER2 in northern states and 14.3 SEER2 for smaller split systems in southern and southwestern states.

Is a higher SEER2 worth the extra cost?

In hot climates with high electricity rates and long run times, a higher SEER2 often pays back. In mild climates the savings are smaller.