If you’re scratching your head at what HSPF and HSPF2 mean for your heat pump, you’re not alone. The shift to HSPF2 ratings in 2023 has left many homeowners confused about how the updated heating seasonal performance factor impacts their home heating. At Watkins Heating & Cooling, we’re here to clear things up with a simple guide on what HSPF stands for, how it differs from HSPF2, and why it matters for your heat pump in 2025.

Want to learn more about how heat pumps work? Check out our page here for a deeper dive into how these systems work for both heating and cooling.

Curious how heat pumps stack up to furnaces and electric heaters in the winter? Check out our charts on heat pump performance compared to other HVAC systems.

What is HSPF?

HSPF, or Heating Seasonal Performance Factor, is a rating that measures how efficiently a heat pump warms your home during the fall and winter months (heating season). The higher the HSPF, the more energy efficient the heat pump – less electricity is used to heat your home. This means more cost savings on your energy bills!

For example, a heat pump with a 9.0 HSPF is more energy efficient than one with a 7.5 HSPF – producing the same amount of heat with less electrical energy.

HSPF was created by the U.S. Department of Energy (DOE) and standardized by the Air Conditioning, Heating, and Refrigeration Institute (AHRI), to make sure all heat pumps perform consistently. These tests simulate average U.S. outdoor temperatures during the heating season, and use home variables like indoor temperature and humidity. The result is a single number to help you compare how well different heat pumps will perform in the cold, whether they’re split system heat pumps or single package units.

Don’t forget – heat pumps also cool your home in the summer! While HSPF tells us the heating efficiency, their cooling efficiency is measured by SEER just like an air conditioner (Seasonal Energy Efficiency Ratio). To learn more about SEER cooling efficiency and the updated SEER2 ratings, check out our post here.

Another important efficiency rating to remember in this conversation is AFUE. You can learn more about AFUE here, a rating specific to furnaces.

What is HSPF2?

HSPF2 is the updated version of HSPF, introduced by the Department of Energy (DOE) in 2023, to measure energy efficiency more accurately.

Why the change? It’s all part of the U.S. government’s push for the HVAC industry to make homes more energy efficient. New standards were put into the testing that account for real-world factors, mostly external static pressure, which is your ductwork’s resistance to airflow. By extension, they are highlighting the efficiency of the indoor fan in your furnace or air handler. This new testing protocol is called “M1.” The old HSPF tests used a low 0.1” w.g. static pressure, but HSPF2 uses a tougher 0.5” w.g. to mimic actual ducted split system setups in homes, not just a bench test in a lab.

The new HSPF2 number gives us a more reliable picture of a heat pump’s everyday energy efficiency, including energy used by your indoor blower.

The DOE predicts that the shift to HSPF2 systems will save U.S. homeowners billions in energy costs over the next 30 years, pushing the HVAC industry toward more efficient indoor blower motors.

Have an old heat pump system? No need to worry about the new number until you start shopping for a new one. Any existing heat pumps made before 2023 will still use the HSPF rating, but all new heat pumps from then on will only display HSPF2 ratings.

How to Convert HSPF to HSPF2

HSPF to HSPF2 conversion is fairly simple. For a very close estimate of the new HSPF2 number, simply multiply the old HSPF number by 0.85. This is the best method we have for telling what an old heat pump’s efficiency would be under the new, stricter testing conditions. This conversion isn’t exact due to additional factors like system design, but it’s a very close guide. Our HSPF to HSPF2 rating chart below lets you look up your HSPF rating and see its HSPF2 equivalent for precise energy efficiency conversions:

This chart is especially handy for those trying to see how their older model stacks up. If you’re shopping for a new system check out our Heat Pump Pricing page to find the right system for your budget.

How Is HSPF Calculated

HSPF is calculated by taking a heat pump during a typical U.S. heating season and dividing its total heating output (in BTUs) by the electrical energy used (in watt-hours). The formula is:

HSPF = Total Seasonal Heating Output (BTUs) / Total Seasonal Electrical Energy (Watt-Hours)

HSPF2 uses the same formula but applies the updated M1 testing conditions, ensuring the efficiency includes the electricity to move air through a typical duct system, not just lab conditions. A higher HSPF2 means the heat pump delivers more heat with less electricity, maximizing cost savings.

Is HSPF2 Better Than HSPF?

Not exactly. A heat pump with an HSPF2 rating doesn’t mean that unit is more energy efficient than a system with just HSPF – it just means the efficiency was measured more accurately. It’s all about the testing procedures. HSPF2 uses harsher testing conditions to better mimic how heat pumps perform in your home.

As you can see in the chart above, this harsher testing means HSPF2 ratings are slightly lower than HSPF for the exact same heat pump unit. For example, the 2022 Trane XR15 heat pump had an 8.8 HSPF. But under HSPF2 testing, it’s now rated around 8.4. The heating efficiency didn’t change—just the way the indoor blower was measured.

The testing changes from the old HSPF to new HSPF2 include:

• External static pressure: Increased from 0.1” to 0.5” w.g., reflecting real ductwork resistance in split system heat pumps.
• Real-world conditions: Tests use more precise outdoor temperatures, system runtime, and maintenance needs to mimic actual heating season performance.
• Accurate energy consumption: HSPF2 ratings measure how efficiently a heat pump uses electrical energy by accounting for typical homeowner usage patterns and system cycling.

HSPF to COP: What’s the Connection?

When researching heat pumps, you might come across COP (Coefficient of Performance). COP measures how many watts of heat was produced divided by how many watts of electricity was used. A typical rating of 3 indicates that a heat pump consumes 1 unit of power and produces 3 units of heat. Because it’s moving heat from outside to indoors, it’s 300% efficient, or 3 times better than a resistance electric heater!

Unlike HSPF, which measures a heat pump’s efficiency over the entire heating season, COP shows how efficiently it converts electricity to heat at a specific standard temperature (typically 47°F). You can’t convert HSPF (or HSPF2) to COP since COP is a spot measurement and HSPF2 is a weighted seasonal average.

As a rough estimate, you could say that 8.8 HSPF ≈ 2.58 COP, but that’s just a rough ballpark. Two heat pumps may have the same COP at 47°F, but one is better at cold temperatures. This is reflected in the HSPF2, but not the COP. Manufacturers provide exact COP values at specific temperatures in spec sheets for the engineers. So if you’re comparing systems, don’t get hung up on COP numbers—HSPF2 tells you how the unit will perform across an entire Ohio winter.

HSPF2 Regional Regulations

The Department of Energy (DOE) now sets efficiency standards by region, recognizing that heating and cooling needs vary by area. In colder North Region states like Ohio, heat pumps need to have higher HSPF2 ratings for efficiency incentives because of colder temperatures. Warmer states in the Southwest and Southeast Region focus on cooling efficiency, requiring higher a seasonal energy efficiency ratio (SEER2).

Since January 1, 2023, all new heat pumps must meet HSPF2 minimums. In Ohio, the minimum requirement is 7.5 HSPF2 (~8.8 HSPF).

Regional standards can complicate inventory for manufacturers. For example, a heat pump sold in Ohio may meet the 7.5 HSPF2 requirement, but not the Southwest’s stricter 14.3 SEER2 requirements. This regulatory confusion has added to the replacement cost for homeowners.

HSPF2 and Tax Credits in 2025

The 2022 Inflation Reduction Act offers a $2,000 tax credit for efficient heat pumps. In Ohio in 2025, your heat pump needs to have 8.1 HSPF2 and 15.2 SEER2 to earn tax credits. It also has to meet Energy Star Cold-Climate status which means high heating output at low temperatures. Qualifying heat pumps include the Trane XV20i and Trane XV18.

Remember to always request an AHRI certificate when you get a new heat pump to verify its efficiency ratings, and keep it for your CPA to avoid audit issues down the road.

UPDATE: The “Big Beautiful Bill” was signed into law July 4th, 2025 ending the 25C tax credit early. HVAC must now be INSTALLED by December 31st, 2025 to qualify.

Learn about all 2025 tax credits you can get here.

How HSPF2 Impacts Costs

The HSPF2 transition didn’t change heat pump technology, but it did raise costs. Manufacturers like Trane faced expenses re-testing split system heat pumps and discontinuing low-efficiency models, passing costs on to consumers. A 2025 8.1 HSPF2 heat pump certainly costs more than a 2022 8.8 HSPF model though the real-world energy usage is the same. Hopefully over time, manufacturers will innovate more efficient blowers to optimize for the test, resulting in real energy savings under real-world conditions. Compare heat pump costs using our pricing calculator.

Choosing Your Heat Pump

The HSPF to HSPF2 shift is a win for energy efficiency, giving you a clearer picture of how your heat pump will perform before you buy. Whether you’re upgrading your HVAC system or trying to learn more about your old unit, HSPF2 ratings help you make informed decisions for cost savings and comfort.

At Watkins Heating & Cooling, we’re transparent about efficiency ratings and committed to finding the right system for your home AND your budget. Beware of contractors using outdated HSPF numbers to mislead you. Explore our Trane Heat Pump Products to see specific Trane options. Ready to upgrade? Reach out to our HVAC professionals below to find the perfect heat pump system for your home!