SEER2, EER2 and HSPF2 Explained:
What the Ratings on a Quote Mean

The Three Numbers in One Paragraph

SEER2 is cooling efficiency averaged over a whole cooling season: Btu of heat removed per watt-hour of electricity. EER2 is cooling efficiency at one hot condition, a 95°F outdoor temperature, as defined in 10 CFR 430.32.HSPF2 is heating efficiency over a heating season, Btu of heat delivered per watt-hour, so it appears only on heat pumps. For all three, higher means less electricity for the same comfort.

Why the "2": The 2023 Test Change

From January 1, 2023, the U.S. Department of Energy (DOE) moved central air conditioners and heat pumps to a new test procedure. It tests at a higher external static pressure, closer to the air resistance of real ductwork, so the same unit scores lower in SEER2 than it did in SEER. That is why the numbers in the DOE rules look different before and after 2023: a split air conditioner made from 2015 to 2022 needed 13 SEER, and one made from 2023 needs 13.4 SEER2 (10 CFR 430.32(c)(1) and (c)(5)).

The practical rule: compare SEER2 with SEER2 and HSPF2 with HSPF2. If one quote gives an old-style SEER number and another gives SEER2, ask the first for the SEER2 figure before you compare them.

DOE Minimums Since January 1, 2023

Heat pump minimums are national and depend on when the unit was made. Air conditioner minimums differ by region, and the regional ones depend on where and when the unit is installed: an air conditioner that meets only the northern minimum cannot be installed in the Southeast or Southwest from January 1, 2023 (10 CFR 430.32(c)(6), read October 22, 2026).

• Southeast: Alabama, Arkansas, Delaware, Florida, Georgia, Hawaii, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia, the District of Columbia, Puerto Rico and the U.S. territories
• Southwest: Arizona, California, Nevada and New Mexico
• North: every other state, where the 13.4 SEER2 national minimum is the floor for a split air conditioner
• Southwest EER2 for split air conditioners: 11.7 below 45,000 Btu/h and 11.2 at 45,000 Btu/h and up, dropping to 9.8 for units of 15.2 SEER2 or more

The region follows the installation address: a split air conditioner installed in Dallas or Miami has to meet the Southeast minimum, one in Phoenix or Sacramento the Southwest minimums, and one in Chicago the national floor.

These are floors, not targets. They also say nothing about your current system: the rules cover new equipment, and an existing air conditioner or heat pump can keep running and be repaired.

ENERGY STAR Levels

ENERGY STAR sets higher marks. The heat pump figures below come from itsair-source heat pump key product criteria (read October 22, 2026), and the air conditioner figures from theVersion 6.2 central air conditioner and heat pump specification.

For cold regions, ENERGY STAR adds a separate cold-climate level for heat pumps: at least 8.5 HSPF2 for ductless split systems and 8.1 HSPF2 for ducted split and single-package systems, all at 15.2 SEER2 or more. It also requires a test at 5°F outdoors, where the unit must reach a coefficient of performance of at least 1.75 and keep at least 70% of the heating capacity it has at 47°F. If you live where winters stay below freezing for weeks, those 5°F figures tell you more than HSPF2 does.

CEE Tiers

Above ENERGY STAR sit the tiers of the Consortium for Energy Efficiency (CEE), a group of efficiency program administrators. Its residential heating and cooling levels, revised with effect from January 1, 2025, have Tier 1, Tier 2 and an Advanced Tier aimed at cold-climate split heat pumps, with two paths: one for heating-dominated homes and whole-home electrification, the other for cooling-dominated and dual-fuel homes (CEE, December 16, 2024). Many utility efficiency programs set their thresholds from these tiers, so if your utility names a CEE tier, check its current table before you choose a model.

From Rating to Running Cost

The ratings convert directly into electricity, because each is a ratio of heat moved to electricity used.

Cooling: divide by SEER2

Seasonal cooling electricity in kWh is the cooling your home needs in Btu divided by SEER2 × 1,000. Because the load is the same whichever unit you buy, the saving between two units is a simple ratio: a 16 SEER2 unit uses 13.4 ÷ 16, about 84%, of the electricity a 13.4 SEER2 unit uses, so roughly 16% less. A 20 SEER2 unit uses 67% of it. The kWh you save in dollars depends on your electricity price and on how many hours your system cools each year, which is why the same upgrade can repay itself quickly in a hot climate and slowly in a mild one.

Heating: divide HSPF2 by 3.412

HSPF2 divided by 3.412 gives the heat pump's average seasonal coefficient of performance: how many units of heat it delivers per unit of electricity. The DOE minimum of 7.5 HSPF2 works out to about 2.2, and 9 HSPF2 to about 2.6. Our heating cost calculator turns an HSPF2 figure, your state's 2024 energy prices and your region's typical heating use into a yearly estimate, and the heat pump vs gas furnace cost by state page compares the same figures across all states.

One caution: these are laboratory ratings. Real consumption also depends on the climate, the ductwork, the sizing of the equipment and the quality of the installation. A unit that is oversized or installed on leaky ducts will not deliver its rating. Our guide to what size HVAC system you need covers how the size is worked out.

Reading the Ratings on a Quote

• Check that the rating is SEER2 and HSPF2, not old-style SEER and HSPF
• Ratings belong to a matched outdoor and indoor unit, so the quote should list the model number of each
• In the Southeast and Southwest, check the air conditioner meets the regional SEER2 minimum, and in the Southwest the EER2 minimum
• In a cold climate, ask for the heat pump’s heating capacity and coefficient of performance at 5°F
• When two quotes differ in efficiency, work out the kWh difference with the ratios above before weighing the price gap

For what each kind of job involves, see our guides to AC installation, heat pump installation and mini-split installation. For prices, see HVAC installation cost in 2026, and for choosing between system types, heat pump vs. central air.

Sources

• U.S. Department of Energy standards, 10 CFR 430.32(c): central air conditioners and heat pumps (via Cornell LII, read October 22, 2026)
• ENERGY STAR: air-source heat pump key product criteria, including cold-climate criteria (read October 22, 2026)
• ENERGY STAR Version 6.2 central air conditioner and heat pump specification
• Consortium for Energy Efficiency: 2025 performance requirements for HVAC and water heaters (December 16, 2024)