Efficiency
SEER2
A seasonal cooling-efficiency rating used for central air conditioners and heat pumps.
What is SEER2?
SEER2 stands for Seasonal Energy Efficiency Ratio 2. It represents seasonal cooling efficiency under the U.S. Department of Energy test procedure for covered central air conditioners and heat pumps. The rating is expressed in BTU of cooling per watt-hour of electrical energy, so a higher SEER2 generally indicates less electrical energy is needed to deliver the same standardized seasonal cooling output.
SEER2 replaced the older SEER representation for newly rated covered equipment as DOE moved to updated test procedures beginning in 2023. The newer procedure includes revised external static-pressure conditions intended to better represent installed duct-system resistance.
SEER2 is a laboratory rating for standardized comparison. It is not a guarantee of a home's utility bill because actual energy use also depends on climate, thermostat settings, sizing, installation quality, duct losses, maintenance, and part-load operation.
Why it matters
SEER2 is useful when comparing the seasonal cooling efficiency of eligible systems, but the rating should be attached to the certified equipment combination rather than assumed to belong to one indoor or outdoor component by itself.
Formula / Conversion
SEER2 = seasonal cooling output (Btu) ÷ seasonal electrical energy input (Wh)
Sources
HVACBird prioritizes government standards bodies, federal test procedures, and recognized HVAC certification organizations for technical definitions.
Electronic Code of Federal Regulations
Federal test-procedure requirements for central air conditioners and heat pumps, including SEER2, EER2, and HSPF2.
U.S. Department of Energy
DOE guidance explaining SEER2 and HSPF2 ratings and the 2023 testing transition.
Air-Conditioning, Heating, and Refrigeration Institute (AHRI)
AHRI guidance on certified matched systems, reference numbers, and third-party performance verification.
Related HVAC Terms
EER2
A cooling-efficiency rating measured at a specified full-load test condition.
HSPF2
A seasonal heating-efficiency rating for air-source heat pumps.
COP
A dimensionless ratio comparing useful heating or cooling delivered with the work supplied to the system.
Matched System
A specific combination of HVAC components evaluated together as one system.
AHRI Certified Reference Number
A unique identifier used by AHRI for a certified HVAC equipment combination or product record.