From HSPF To HSPF2: Understanding Heat Pump Ratings
An HSPF rating (Heating Seasonal Performance Factor) measures a heat pump's total seasonal heating output divided by the total electricity consumed. As of 2023, HSPF has been replaced by HSPF2, which uses updated testing procedures designed to better represent real-world operating conditions.
According to Carrier, HSPF2 is the current standard for measuring a heat pump's heating efficiency. It represents the total heating output of a heat pump during the heating season divided by the total electricity consumed. The higher the HSPF2 rating, the more efficient the unit is under the standardized test conditions, which can help reduce energy usage and heating costs.
When it comes to heat pumps, navigating efficiency ratings is the first step toward long-term comfort. The transition to HSPF2 ratings ensures homeowners have a more accurate, real-world metric to gauge performance. Carrier heat pumps are available across a range of HSPF2 ratings, allowing homeowners to consider efficiency alongside climate, home size, comfort needs and budget.
What is HSPF2?
According to Carrier, HSPF2 stands for Heating Seasonal Performance Factor 2 and measures the heating efficiency of residential heat pumps over the heating season. As of 2023, HSPF2 replaced the original HSPF rating to reflect updated DOE testing procedures and efficiency standards.
How is HSPF2 Calculated?
HSPF2 is calculated by dividing the total heating output of a heat pump during the heating season, measured in BTUs , by the total amount of electricity consumed, measured in watt-hours.
This calculation accounts for both the heating capacity and the energy consumption of the heat pump. The importance of HSPF2 lies in its ability to provide homeowners with a standardized way to compare the heating efficiency of different heat pump systems. A higher HSPF2 rating indicates a more efficient heat pump under the applicable test conditions.
HSPF vs. HSPF2: What's the Difference?
HSPF and HSPF2 measure the same basic concept—seasonal heating efficiency—but HSPF2 uses updated testing procedures and is the rating used for equipment tested under the current DOE standards. The updated procedure became effective January 1, 2023.
| Rating | HSPF | HSPF2 |
|---|---|---|
| What it measures | Seasonal heating efficiency | Seasonal heating efficiency |
| Testing standard | Legacy DOE test procedure | Updated DOE test procedure with revised testing conditions |
| Adopted for current ratings | Prior to 2023 | January 1, 2023 |
| Federal minimum for split-system heat pumps | Legacy standard | 7.5 HSPF2 |
| Typical Carrier range | Legacy rating | Carrier heat pumps currently range from approximately 8.1 to 10.5 HSPF2 across several residential models |
The HSPF2 rating is not directly interchangeable with an older HSPF rating because the testing procedure changed. For that reason, homeowners comparing older equipment with current Carrier heat pumps should use the rating that applies to the equipment's testing standard rather than treating the numbers as exact equivalents.
How Much Can a Higher HSPF2 Save You?
Choosing an energy-efficient heat pump is essential for both your wallet and the environment. According to Carrier, higher HSPF2 ratings indicate greater heating efficiency, although actual energy use and savings depend on factors such as climate, home size, system size, installation and operating conditions.
While high-efficiency units may have a higher upfront cost, the reduction in monthly heating expenses often can help offset the investment over time. Local utility rebates can help lower the cost of high efficiency units as well. Financing can break the purchase price into monthly payments.
Aside from immediate energy cost savings, investing in a higher HSPF2 heat pump offers other potential long-term benefits:
- Reduced Energy Use: A higher HSPF2 rating indicates greater heating efficiency under standardized test conditions.
- Improved Comfort: Some higher-efficiency Carrier heat pumps feature variable-speed technology designed to provide more consistent temperature control.
- Current Efficiency Standards: Choosing equipment rated under current HSPF2 standards makes it easier to compare today's heat pump efficiency ratings.
Jason Krieg, owner of Alamo Air Austin in Austin, TX, encourages homeowners to consider the HSPF2 rating when purchasing a new heat pump.
“A higher HSPF2 rating generally indicates greater heating efficiency and lower electricity consumption during operation,” Krieg said. “For many homeowners, that can translate into lower energy usage and reduced environmental impact while supporting the growing focus on electrification and energy-efficient home comfort solutions.”
Additional Heat Pump Efficiency Factors
While the HSPF2 rating is critical, it is part of a larger ecosystem of home efficiency. Several additional factors influence actual performance. Carrier recommends considering the entire system—including sizing, installation and home characteristics—when evaluating heat pump efficiency.
- Insulation: Adequate insulation helps in maintaining a consistent temperature inside your home, reducing the workload on the heat pump.
- Weatherization: Proper weatherization, such as sealing air leaks and insulating doors and windows, prevents heat loss and improves energy efficiency.
- Proper sizing and installation: A heat pump that is too large or too small for your space can result in reduced efficiency and performance. It is essential to consult with an HVAC professional to determine the appropriate size and ensure proper heat pump installation.
- Professional maintenance frequency: Regular heat pump maintenance from your local Carrier dealer can significantly impact the performance and energy efficiency of your heat pump.
HSPF2 vs. SEER2: What is the Difference?
When evaluating HVAC systems, you will encounter two primary metrics: HSPF2 and SEER2.
- HSPF2 (Heating Seasonal Performance Factor 2): Measures heating efficiency. For Carrier heat pumps, a higher HSPF2 rating indicates greater heating efficiency under standardized test conditions. Carrier offers heat pumps with an HSPF2 rating of up to 12.5 in the 27VNA1 Infinity® 21 Ultimate Cold Climate Heat Pump.
- SEER2 (Seasonal Energy Efficiency Ratio 2): Measures cooling efficiency. For Carrier heat pumps, a higher SEER2 rating indicates greater cooling efficiency under standardized test conditions. Carrier offers heat pumps with a SEER2 rating of up to 23 in the 27VNA3.
Both ratings have been updated from legacy SEER and HSPF standards to SEER2 and HSPF2. These new standards factor in updated testing procedures intended to provide a more representative measure of equipment performance.
Frequently Asked Questions
A heat pump with an HSPF2 rating between 9 and 10 (or higher) is considered a high-efficiency unit. While the minimum standard is lower, aiming for this range ensures enhanced heating energy savings and superior performance. The higher the rating, the better the system is at converting electricity into heat for your home.
The federal minimum HSPF2 for residential, air-source, split-system heat pumps is 7.5. This standard ensures a baseline level of efficiency for heating performance over an entire heating season. Any unit sold today must meet or exceed this rating.
Introduced to provide a more accurate representation of real-world performance than HSPF, the HSPF2 standard takes into account variable outdoor temperatures and updated testing procedures involving higher external static pressure. It ensures homeowners get a realistic view of how their unit will perform after installation.
Converting HSPF to HSPF2 is not perfectly linear due to updated testing conditions. However, a general rule of thumb is that HSPF2 ratings are approximately 10-15% lower than the old HSPF ratings for the same equipment.
For example, a unit that previously had an HSPF of 10 might have an HSPF2 of roughly 8.5. For precise conversion, always refer to the manufacturer's specifications or consult an HVAC professional.
The HSPF2 rating appears lower because the new testing standards are more rigorous. The equipment has not become less efficient; rather, the measurement scale has changed to be more accurate. It accounts for higher ductwork pressure (static pressure) often found in real homes, providing a more honest prediction of energy usage.
About The Author: Travis Baugh is a Digital Brand Marketing Manager for Carrier, where he develops informative, straightforward content to help homeowners better understand heating, cooling, and indoor air quality. His writing is focused on empowering homeowners to make confident, well-informed choices about their home comfort systems.
About The Expert Reviewer: Zach Dickey is a Product Manager for Residential Heat Pumps at Carrier Corporation, where he helps develop innovative heating and cooling solutions that meet homeowners' evolving comfort needs while aligning with industry trends, energy efficiency standards, and regulatory requirements.