Quick answer
SEER measures cooling efficiency; HSPF measures heating efficiency; higher numbers mean lower operating costs 1. SEER is Seasonal Energy Efficiency Ratio; HSPF is Heating Seasonal Performance Factor 1.
How it works
SEER and HSPF are the two numbers you'll see on every heat pump's yellow EnergyGuide label. They measure efficiency in different seasons—SEER for cooling, HSPF for heating. The higher the number, the less electricity the unit uses to keep you comfortable.
SEER stands for Seasonal Energy Efficiency Ratio. It's the total cooling output during a typical cooling season divided by the total electric energy input over the same period. In plain terms, a 20 SEER unit uses half the electricity of a 10 SEER unit to deliver the same cooling.
HSPF—Heating Seasonal Performance Factor—works the same way but for heating. It divides the total heating output by the total electricity consumed over a heating season. Because heat pumps move heat rather than generate it, even a modest HSPF rating can beat the efficiency of electric resistance heat.
In 2023, the Department of Energy introduced updated testing procedures that gave us SEER2 and HSPF2. These new metrics reflect more realistic operating conditions—higher external static pressure in the ductwork, for example. Because the test is tougher, the numbers come out lower. SEER2 ratings are about 5% lower than the old SEER ratings 2. HSPF2 ratings drop roughly 15% compared to the original HSPF 2. So a unit that was rated 16 SEER might now show 15.2 SEER2, and an 8.5 HSPF unit could become a 7.2 HSPF2.
Current minimum HSPF2 ratings start at 7.5, and high-efficiency models can exceed 10 3. When you're comparing units, make sure you're looking at the same metric—mixing SEER with SEER2 or HSPF with HSPF2 will give you a misleading picture.
When this matters for you
Efficiency ratings translate directly into your utility bills. A higher SEER or HSPF means the heat pump uses less electricity to do the same job. In a cooling-heavy climate like Clearwater, FL, upgrading from a 14 SEER to a 21 SEER heat pump can save about $364 per year in cooling costs alone 4. That’s because the 14 SEER unit would consume roughly $1,004 annually, while the 21 SEER unit would use about $640 4.
But the payoff isn’t just about the sticker number. How much you actually save depends on your local climate, electricity rates, and how well your home is insulated. In milder regions, the difference between a 15 SEER and a 20 SEER unit might be smaller, while in places with brutal summers or high electric rates, the savings stack up faster. The same logic applies to heating: a higher HSPF matters most if you rely on the heat pump through cold winters.
When you’re comparing quotes, don’t just look at the upfront cost. Run the numbers on operating costs over the unit’s typical 15-year lifespan. A unit that’s $1,200 more expensive but saves $150 a year pays for itself in eight years—and keeps saving after that. If you’re staying in the home long-term, the higher efficiency usually wins.
Standards and codes
If you're shopping for a new heat pump, you'll run into a tangle of efficiency numbers and regional rules. The US Department of Energy sets minimums that vary by location and equipment type. For residential units, the baseline is SEER2—a newer, stricter test procedure that replaced the old SEER metric. In the northern US, new heat pumps must hit at least 13.4 SEER2, while the southeast and southwest regions require 14.3 SEER2 1.
Split system heat pumps face tighter rules in some areas. As of January 1, 2023, the Southwest region demands 14.3 SEER2 and 7.5 HSPF2 5. The Southeast region has the same split-system requirement: 14.3 SEER2 and 7.5 HSPF2 6. Packaged heat pumps—where the whole system lives in one outdoor cabinet—have a lower federal floor: 13.4 SEER2 and 6.7 HSPF2 5.
If you're aiming for an ENERGY STAR label, the bar is higher. Certified heat pumps need a SEER2 of 15.2 or above 1. They also must deliver an HSPF of at least 8.5 and an EER of 12 or higher 7. For context, the current federal minimum HSPF is 7.7, though high-efficiency models can reach 10+ HSPF 8. That spread matters in cold climates where heating performance eats up most of your energy bill.
⚠️ Warning: Installing a unit that meets only the federal minimum in a region with stricter local codes can fail inspection and void rebates. Always check your state's current requirements before buying.
Still confused after comparing labels? A common snag is mixing up SEER and SEER2, or HSPF and HSPF2. The "2" versions use a more realistic test that accounts for external static pressure, so the numbers don't convert 1:1. If a contractor quotes an older SEER rating, ask for the SEER2 equivalent—it's what actually counts for code compliance today.
Frequently Asked Questions
What's the difference between SEER and SEER2? SEER2 uses a more realistic testing procedure that accounts for higher external static pressure in ducted systems, so the number you see is typically about 5% lower than the older SEER rating. A unit that was labeled SEER 16 under the old test might show SEER2 around 15.2 2. The new metric gives you a truer picture of how the system will perform in your actual home.
What's the difference between HSPF and HSPF2? HSPF2 follows the same updated testing protocol as SEER2, and the drop is more pronounced—about 15% lower than the old HSPF number. A heat pump that carried an HSPF 10 rating under the old test could land around HSPF 8.5 under the new standard 2. When you're comparing older and newer models, make sure you're looking at the same rating system so you don't accidentally think a new unit is less efficient than it really is.
Do higher SEER and HSPF ratings always save me money? Higher ratings mean the unit uses less electricity to deliver the same amount of heating or cooling, so your utility bills should go down. But the actual savings depend on your local climate, how well your home is insulated, and what you're replacing. In a mild climate, jumping from a 14 SEER to a 20 SEER unit might not pay back the upfront cost difference as quickly as it would in a hot, humid region where the air conditioner runs for months. An experienced plumber or HVAC tech can run a load calculation and help you weigh the numbers for your specific house.
Are there minimum efficiency requirements for heat pumps? Yes, and they changed on January 1, 2023, when the Department of Energy switched to SEER2 and HSPF2 metrics. The new federal minimums vary by region. For example, in the Southeast, split-system heat pumps must meet at least 14.3 SEER2 and 7.5 HSPF2 6. ENERGY STAR certified units go higher: as of 2025, they need to hit 15.2 SEER2 and 8.1 HSPF2 for most split systems 7. Always check your local code, because some states set their own higher bars.
Can I just convert an old SEER rating to SEER2? There's no exact formula because the test conditions are different, but the 5% rule of thumb for SEER and 15% for HSPF is a decent ballpark estimate. If you're trying to compare an older unit to a new one on the showroom floor, ask the contractor for the AHRI certificate—it lists both the legacy and the new ratings for many models, so you can make an apples-to-apples comparison.