​​​​HVAC efficiency basics: Key ratings Minnesota homeowners should understand​

Minnesota experiences wide temperature swings and periods of extreme weather, which can increase the demand placed on heating and cooling equipment. In recent years Minnesota has seen its windiest year in over 40 decades (2022), possibly its most extreme-weather month ever (December 2023), its warmest year ever recorded (2024) and its worst air quality day ever recorded​ (June 3, 2025). 

Higher demand can lead to increased energy use, which makes efficiency ratings a relevant factor when comparing HVAC systems. These ratings describe how equipment performs under standardized test conditions and offer a consistent basis for evaluating options in climates with large seasonal variations.

The most important HVAC efficiency ratings

SEER and SEER2 (Seasonal Energy Efficiency Ratio)

Dating back to the 1970s, SEER was the original federally recognized efficiency metric for residential air conditioners and heat pumps in the U.S. Short for Seasonal Energy Efficiency Ratio, SEER measures cooling efficiency over an average season, dividing the total BTUs used for cooling over a season by the total amount of energy consumed (in watt-hours) over the same time period. 

In 2023, to better simulate real-world conditions like static pressure in ducts, SEER2 became the federal standard. The SEER2 minimum efficiency score for all new residential central air conditioning and air-source heat pump systems is now 13.4 in northern states like Minnesota. A score of 17-20 is considered high-efficiency.

However, because heating degree days (HDDs) far outnumber cooling degree days (CDDs) in Minnesota, homeowners who are evaluating new systems often place additional attention on heating performance metrics.

EER and EER2 (Energy Efficiency Ratio)

EER (Energy Efficiency Ratio) measures cooling efficiency at a single peak condition–typically 95°F outdoors, 80°F indoor and 50% humidity. It provides consumers a glimpse of how an AC or heat pump might perform on a hot summer day at peak load. EER2 is the updated version introduced by the DOE in 2023, using revised test procedures aligned with SEER2 changes.

Federal minimum EER requirements apply primarily in the Southwest region, where cooling loads are higher. For Minnesota, EER and EER2 values can still be useful for comparing how equipment performs under peak-load test conditions. These ratings are typically found in manufacturer specifications or product documentation.

SEER vs EER

AFUE (Annual Fuel Utilization Efficiency)

AFUE (Annual Fuel Utilization Efficiency) measures the percentage of fuel energy that a furnace converts into heat under standardized test conditions. 

Older models may operate with lower AFUE values, while newer furnaces often reach 80–85%. ENERGY STAR® designates gas furnaces with AFUE ratings of ≥ 95% as high-efficiency in northern states such as Minnesota, based on program criteria. These models can save up to $120 per year in energy costs, according to the Environmental Protection Agency (EPA).  

HSPF2 (Heating Seasonal Performance Factor)

HSPF2 (Heating Seasonal Performance Factor 2) measures the total heat output of a heat pump during the heating season relative to the electricity it uses under updated DOE test procedures.

Taking the total heat output (in BTUs) and dividing by the total electricity consumed (in watt-hours) over a heating season reveals a heat pump’s HSPF2 score, which typically falls between 7.5 and 10. Heat pumps with HSPF2 above 8.0 are considered highly efficient.

In colder climates, heat pumps have a balance point at which their heating capacity no longer meets a home’s load. In those instances, backup heat solutions such as a dual-fuel system where a furnace takes over for the heat pump may become necessary.

Thus a complete HVAC efficiency picture should take into account the efficiency of the backup system, as well as the metrics for measuring when they may be needed. The latter includes:

• the balance point temperature: the outdoor temperature where the heat pump can no longer meet the home’s heating load by itself; and
• the coefficient of performance (COP): the ratio of how many units of heat you get per unit of energy in, which drops as the temperature drops.  ENERGY STAR lists a COP of ≥ 1.75 at 5°F as part of its cold-climate heat pump criteria.​​​
  
  

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Beyond the ratings: What else impacts HVAC efficiency

Professional installation

Efficiency ratings are based on standardized test conditions, which assume proper installation. Incorrect sizing, airflow issues, or improper setup can reduce a system’s ability to operate as tested. Sub-optimal installation can lead to energy usage as high as 30% over what it should be.  

Home Service Plus provides professional installation services in Minnesota and follows manufacturer specifications and industry standards during equipment setup.

System sizing and home insulation

System size and home insulation influence how often an HVAC system operates and how much energy it uses. Undersized systems may run for longer periods, and oversized systems may cycle on and off more frequently. Inadequate insulation can also increase heating and cooling demand by allowing heat transfer between indoor and outdoor spaces.

Ductwork design and condition

Ductwork condition can affect airflow and energy use. Leaks or poorly designed duct layouts can reduce the efficiency of heating and cooling systems by allowing conditioned air to escape or restricting airflow.

Inspecting ductwork before installing new equipment helps confirm that the distribution system supports the expected performance of the HVAC unit.

Maintenance and filter changes

Routine maintenance, including replacing or cleaning air filters, supports proper airflow and can help HVAC systems operate as designed under test conditions. 

HSP offers maintenance services in Minnesota, including filter replacement as part of scheduled system inspections.​

What’s considered high-efficiency HVAC equipment in Minnesota?