HVAC efficiency calculators

The Department of Energy rolled out the M1 test procedure in 2023, and the efficiency numbers on HVAC nameplates changed overnight. SEER became SEER2. HSPF became HSPF2. EER became EER2. The physical equipment did not change, but the test conditions got harder, so the same air conditioner that used to be rated SEER 16 is now rated SEER2 15.2.

That four-to-six-percent rating drop confuses everyone shopping for a new system. A homeowner sees an old SEER 16 unit at the supply house clearance pile and a new SEER2 16 unit at the dealer and thinks they are equivalent. They are not. The new unit is meaningfully more efficient, and the conversion math here makes that visible.

Heat pumps got the same treatment with HSPF to HSPF2. The conversion is slightly different (HSPF2 is roughly 85 percent of HSPF) because the heating test has its own loading profile. EER is also being phased out in favor of EER2 on AHRI listings, though the older EER value is still useful for steady-state hot-day capacity questions.

Beyond the rating conversions, two tools on this page go deeper. The COP calculator lets you check the real coefficient of performance at any outdoor temperature, which is the only honest way to evaluate a heat pump in a cold climate. The annual kWh estimator predicts what your HVAC will actually pull off the meter based on climate zone, equipment efficiency, and house size, which is the number you need for solar sizing or budgeting.