Heating and cooling # HVAC glossary This glossary defines the HVAC acronyms that appear on bids and spec sheets, and marks explicitly which metrics were superseded by which. That last part matters more than it sounds: confusing SEER with SEER2, or R-410A with R-454B, is the single most common error in this category, and it is the one that costs homeowners money. ## Terms and acronyms ### [SEER2](https://hvacbuddy.shop/glossary/seer2/) Seasonal Energy Efficiency Ratio 2 SEER2 is the ratio of total heat removed from the conditioned space over a cooling season to the total electrical energy the equipment consumed over that season, measured under the DOE test procedure required since January 1, 2023. **Replaces:** SEER ### [SEER](https://hvacbuddy.shop/glossary/seer/) Seasonal Energy Efficiency Ratio SEER is the pre-2023 seasonal cooling efficiency metric. Any SEER figure you find in an article written before 2023 is on this scale, which is why it cannot be compared directly against the SEER2 number on a current quote. **Superseded by:** SEER2 ### [EER2](https://hvacbuddy.shop/glossary/eer2/) Energy Efficiency Ratio 2 EER2 is the ratio of cooling capacity in Btu per hour to power input in watts at a high outdoor temperature, on the current DOE test procedure. It matters most in hot-dry climates, which is why the Southwest region carries an EER2 requirement that the other regions do not. **Replaces:** EER ### [EER](https://hvacbuddy.shop/glossary/eer/) Energy Efficiency Ratio The pre-2023 peak-load cooling efficiency metric. **Superseded by:** EER2 ### [HSPF2](https://hvacbuddy.shop/glossary/hspf2/) Heating Seasonal Performance Factor 2 HSPF2 measures how much heat a heat pump delivers over a heating season per unit of electricity consumed, on the DOE test procedure required since January 1, 2023. A higher HSPF2 means less electricity for the same heat. **Replaces:** HSPF ### [HSPF](https://hvacbuddy.shop/glossary/hspf/) Heating Seasonal Performance Factor The pre-2023 seasonal heating efficiency metric for heat pumps. **Superseded by:** HSPF2 ### [AFUE](https://hvacbuddy.shop/glossary/afue/) Annual Fuel Utilization Efficiency AFUE is expressed as a percentage. A 95% AFUE furnace converts 95% of the fuel's energy into heat delivered to the house over a heating season. AFUE was not renamed in 2023 — there is no "AFUE2" — so an AFUE figure from an older article is still on the same scale. ### [COP](https://hvacbuddy.shop/glossary/cop/) Coefficient of Performance COP is an instantaneous ratio at a stated condition, not a seasonal average. A COP of 3 means three units of heat for one unit of electricity. Because COP is quoted at a specific outdoor temperature, a COP figure without its condition tells you almost nothing — this is where cold-climate heat pump claims are most often mis-stated. ### [MERV](https://hvacbuddy.shop/glossary/merv/) Minimum Efficiency Reporting Value MERV runs from 1 to 16 for residential filters. Higher captures more, and also resists airflow more. A filter too restrictive for the system's design static pressure reduces airflow, which hurts capacity and can damage equipment — the tradeoff almost no filter marketing mentions. ### [R-22](https://hvacbuddy.shop/glossary/r-22/) HCFC U.S. production and import of R-22 ended on January 1, 2020, with narrow exceptions for export and for destruction or transformation. ### [R-410A](https://hvacbuddy.shop/glossary/r-410a/) HFC blend R-410A has an EPA exchange value of 2,088, well above the 700 limit that applies to newly manufactured residential air conditioning and heat pump equipment from January 1, 2025. ### [R-454B](https://hvacbuddy.shop/glossary/r-454b/) HFO/HFC blend R-454B has an EPA exchange value of 465, under the 700 limit, which is why it is one of the two refrigerants most new residential systems now ship with. ### [R-32](https://hvacbuddy.shop/glossary/r-32/) HFC R-32 has an EPA exchange value of 675, under the 700 limit. Several manufacturers chose it over R-454B. ## What should a bid show you? Three bids rarely quote the same job, so comparing headline price compares three different things. The one that was done properly shows its work, and you can check it line by line: - Model numbers for the outdoor unit, indoor coil, and air handler or furnace. - The **AHRI reference number** for that exact combination. A rating applies to a matched system, not to an outdoor unit on its own. - The SEER2 and, on a heat pump, the HSPF2 of that combination. - The Manual J result the sizing came from. - The measured static pressure and any duct work included. - The permit, and who pulls it. - Labour warranty, separate from parts, and whether registration is required. [The full red-flags checklist](https://hvacbuddy.shop/hiring/). ## What actually drives the cost? We publish no national average price, and the reason matters: an average across every house, region and system type is not a number you can act on. A replacement that includes duct modification, an electrical upgrade and a permit is a different job from a straight swap, and both read as "system replacement" on a one-page proposal. What actually drives your number: - **Equipment capacity and tier**, which should come from the Manual J rather than the old nameplate. - **The ducts** — whether they can move the air the new equipment needs, and what it costs if they cannot. - **Electrical work**, if a circuit or panel change is required. - **Permit and inspection**, usually required. - **Refrigerant** — current equipment uses R-454B or R-32; remaining pre-2025 R-410A stock may price differently. [What a bid should itemise](https://hvacbuddy.shop/costs/) · [operating cost calculator](https://hvacbuddy.shop/calculators/). ## Which efficiency numbers can you actually compare? If you are comparing efficiency figures, check which generation they belong to first. On January 1, 2023 DOE changed the test procedure and renamed three metrics: SEER became **SEER2**, EER became **EER2**, and HSPF became **HSPF2**. The current procedure measures at a higher external static pressure, much closer to what equipment meets once installed in a real house on real ductwork. DOE is explicit about the consequence: "Although SEER2, HSPF2, and EER2 ratings are similar to ratings using the original metrics, they are not directly comparable. Compliance with the new standards for each model must be determined based on its measured SEER2, HSPF2, or EER2." In practice: a SEER figure from a 2019 article cannot tell you whether a quote reading SEER2 is good, bad or identical. That is why we publish no conversion factor. We do not publish a SEER-to-SEER2 conversion factor. DOE states that ratings on the new metrics are "not directly comparable" to ratings on the original metrics, and that compliance must be determined from the measured SEER2, EER2 or HSPF2 value. Approximate multipliers circulate widely, but they vary by equipment type and configuration, and using one to compare an old article's number against a number on today's quote is how homeowners end up believing they were offered less efficiency than they were. Compare like with like: ask for the SEER2 figure, and check it against the AHRI certificate. The nationwide minimum for a split-system air conditioner is 13.4 SEER2, and for a split-system heat pump 14.3 SEER2 with 7.5 HSPF2. [What each metric measures](https://hvacbuddy.shop/efficiency/) · [minimums by region and state](https://hvacbuddy.shop/efficiency/standards/). ## How is the right equipment size decided? Nearly every persistent comfort problem traces back to equipment size, and size is decided before the first box arrives. The standard is the ACCA **Manual J** load calculation (ANSI/ACCA 2 Manual J - 2016), which totals the heat gain and loss of your specific house: orientation, window area and type, insulation levels, air infiltration, internal gains, and your local design temperature. What a Manual J is *not*: square feet per ton, and not the old unit's tonnage. The first ignores everything that makes one house different from another. The second assumes whoever sized the old equipment got it right, and propagates their error for another fifteen years. Oversized equipment reaches the setpoint and shuts off before it has dehumidified, so the house ends up cold and clammy at the same time. Every start is also the hardest moment in a compressor's life, so wear accelerates. And you pay for the surplus capacity twice — once to buy it and again to run it. Ask for the completed Manual J in writing, not the claim that one was done. [What it contains and how to read it](https://hvacbuddy.shop/sizing/manual-j/). ## How can you verify any of this yourself? Everything regulatory on this site traces to a primary source and carries the date it was read: DOE for efficiency standards, EPA for refrigerants and Section 608, the IRS for tax credits, and ACCA for load calculation. The sources for this page are listed at the end with the date each was consulted. If you find a different figure elsewhere, check two things before deciding which to believe: whether the page says which generation its efficiency metric belongs to, and whether it carries a visible review date. Most of the outdated content in this category fails both tests. By [HVACBuddy Editorial Team](https://hvacbuddy.shop/authors/editorial-team/). Last reviewed: 2026-08-18. HVACBuddy publishes independent information. We do not install or service equipment, we do not dispatch contractors, and we do not sell leads. Nothing here is engineering, tax, or legal advice.