Shopping for a new system means meeting a stack of acronyms. They are useful because they let you compare models on one basis, but they are also easy to over-interpret. Here is what the main ones mean and how to use them sensibly.
SEER and SEER2 (cooling)
SEER stands for Seasonal Energy Efficiency Ratio. It compares the cooling an air conditioner or heat pump provides over a typical cooling season to the electricity it uses. A higher SEER generally means more cooling per unit of electricity. Newer testing procedures introduced SEER2, which is measured under different conditions, so SEER and SEER2 numbers are not directly interchangeable. Compare like with like.
EER and EER2
EER measures efficiency at a specific, hot outdoor temperature rather than over a season. It can be a helpful second number in very hot climates.
HSPF and HSPF2 (heat pump heating)
Heat pumps also heat the home. HSPF, or Heating Seasonal Performance Factor, describes heating efficiency over a season, and HSPF2 is the newer test. Higher is generally better, and cold-climate models are designed for lower outdoor temperatures. Ask what the model delivers at the winter temperatures you actually see.
AFUE (furnaces and boilers)
AFUE, Annual Fuel Utilization Efficiency, is shown as a percentage of the fuel that becomes heat for your home over a season. A higher percentage means less fuel is lost up the flue.
Other features that affect comfort and efficiency
- Single-stage, two-stage and variable-speed operation, which affect how smoothly the system adjusts.
- Thermostat and zoning options.
- Ductwork condition and insulation.
- Your home's insulation, windows and air sealing.
Minimums, labels and incentives
Minimum efficiency requirements are set by regulators and can differ by region and equipment type, and they change from time to time. Some incentive programs have their own requirements. Ask your contractor which standards and any programs apply in your area, and verify details with the program administrator.
How to use this when comparing quotes
- Ask for the make, model and rating of each option and compare the same ratings across quotes.
- Ask how the rating translates to the way you use your home, in general terms, without a guaranteed savings figure.
- Ask about sizing, ductwork and commissioning as part of the quote.
- Compare warranty terms for parts and labor.
Be cautious of any contractor who promises a specific amount of savings. Actual energy use depends on many factors. If you are comparing offers, request free HVAC quotes and use this guide to ask better questions.
A realistic way to think about efficiency
Efficiency is one factor among several. Think about how many hours a year the system will run in your climate, what you pay for energy, how long you plan to stay and how the system will be installed. A modest improvement in rating pays off more in a house that is cooled for most of the year than in one that rarely needs it.
Ask your contractor to explain, in general terms and without a guaranteed number, how different rating options compare for homes like yours. A clear, honest answer is a good sign.
Questions about this topic
What SEER rating should I choose?
It depends on your climate, how much you cool your home, budget and local requirements. A contractor can explain the trade-offs between rating tiers for your situation.
Is SEER2 better than SEER?
SEER2 is a newer testing method, not a better product. Ratings are measured differently, so compare SEER2 numbers with other SEER2 numbers.
This guide is general education. It is not legal, financial, engineering or insurance advice, and licensing, permit and insurance rules vary by state and locality.