SEER2 - seasonal cooling efficiency
SEER2 (Seasonal Energy Efficiency Ratio 2) measures cooling output over a whole season divided by the electricity used - so a higher number means less electricity per season of cooling. It's the headline efficiency figure for air conditioning. Mini splits range from the mid-teens at the budget end to the mid-20s and higher for premium and high-efficiency value units; the U.S. minimum for new systems is in the low 14s.
HSPF2 - seasonal heating efficiency
HSPF2 (Heating Seasonal Performance Factor 2) is the heating equivalent - seasonal heating output divided by electricity used. If you'll heat with the system, this is the number that matters most. Strong mini splits post HSPF2 above 8.5, with the best above 10. In cold climates, weigh HSPF2 (and the low-temperature rating) more heavily than SEER2.
EER2 - efficiency at peak conditions
EER2 is a single-point measurement at a hot design condition (95F), not a seasonal average - it tells you how efficient the unit is when it's working hardest. It's most useful in very hot climates where peak-load efficiency and demand charges matter.
Why the "2" - the 2023 testing change
In 2023 the U.S. Department of Energy switched to a new test procedure ("M1") that measures systems against higher external static pressure - conditions closer to a real installation. The result: SEER2/HSPF2/EER2 numbers run roughly 4-5% lower than the old SEER/HSPF ratings for the same equipment. That's not a worse unit; it's a stricter, more realistic test. Don't compare an old SEER number against a new SEER2 number - use SEER2 vs SEER2.
What counts as a "good" rating
Rough context for mini splits:
- SEER2 ~14-17: budget / entry efficiency.
- SEER2 ~18-21: solid mid-tier.
- SEER2 22+: high efficiency; 25+ is premium territory.
- HSPF2 8.5+: good heating efficiency; 10+ is excellent.
Ratings also vary by size (smaller heads usually rate higher), so compare within the capacity you actually need - sort certified numbers by size in the product finder.
Certified vs marketing numbers
Efficiency is exactly where marketing rounds up. Retail and manufacturer pages sometimes show an "up to" figure that exceeds the unit's own AHRI certificate - the independently verified rating. On this site we publish the AHRI-certified number, and where a banner disagrees with the certificate, the certificate wins. When you compare two systems, make sure you're comparing certified figures, not the biggest number each brand prints.
Higher rating vs lower bill - not the same thing
A higher SEER2 uses less electricity per season, but whether it saves you money depends on your electricity rate, your climate, and how many hours the system runs. A premium-efficiency unit in a mild climate may never pay back its premium; a mid-tier unit run hard in a hot, expensive-power region might. Work your real numbers:
- Operating-cost calculator - the bill for a given rating and rate.
- Payback calculator - when a higher rating pays for itself.
- Electricity usage guide - what drives the bill.
Then see which systems lead on certified efficiency in our most efficient mini splits roundup.
FAQ
What is a good SEER2 rating for a mini split? Mid-teens is entry-level, 18-21 is solid mid-tier, and 22+ is high efficiency, with 25+ being premium. Match the rating to your climate and how much you'll run it.
What's the difference between SEER and SEER2? SEER2 uses a stricter 2023 test (higher static pressure) that's closer to real installs, so SEER2 numbers are about 4-5% lower than old SEER numbers for the same unit. Compare SEER2 to SEER2.
Is SEER2 or HSPF2 more important? SEER2 if you mostly cool; HSPF2 if you heat a lot. Cold-climate buyers should weigh HSPF2 and the low-temperature rating most.
Does a higher SEER2 save money? It uses less electricity per season, but the savings depend on your rate, climate, and runtime - run the payback calculator before paying up for the top rating.