What is SEER (and SEER2)? Cooling efficiency explained
SEER (Seasonal Energy Efficiency Ratio) measures cooling efficiency: seasonal cooling output (BTU) divided by electricity used (watt-hours). SEER2 is the stricter 2023 test version. A heat pump both heats and cools, so its SEER affects your summer bill the way COP/HSPF affect winter. Higher SEER2 (15-25 plus) means cheaper cooling.
SEER vs SEER2
Since 2023, US ratings use SEER2, measured at higher external static pressure, so SEER2 is roughly 4-5% lower than the old SEER for the same unit. Minimum new-equipment SEER2 is 13.4-14.3 depending on region.
Why SEER matters for a heat pump
A heat pump is an air conditioner that can run in reverse. Replacing an old AC plus furnace with one heat pump means the SEER2 sets your cooling cost. A high-SEER2 heat pump can cut summer cooling bills versus an old AC, adding to the heating savings.
SEER does not set heating cost
Heating cost is driven by HSPF2/COP, not SEER. A unit can have a great SEER2 but a modest HSPF2; for a heating-led climate, prioritise HSPF2 and a cold-climate rating.
Frequently asked questions
Is SEER or HSPF more important?
It depends on your climate. In a cooling-dominated South, SEER2 matters more; in a heating-dominated North, HSPF2/COP matters more. A heat pump has both ratings.
What is a good SEER2?
SEER2 of 15-18 is solid for most homes; 20 plus is high-efficiency. Diminishing returns set in unless you run a lot of cooling.
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Last updated: 2026-06-29