Reference
HVAC Glossary
Canonical definitions for HVAC trade terms used across Cheap Cold Air guides — linked to Learn guides and service pages so you have consistent language when reading estimates, comparing options, or planning a system upgrade in Austin.
How to use this glossary
Each term has a short definition you can read in a few seconds, plus a longer detail page with the source (federal code, ACCA standard, utility program), why it matters for an Austin home, and the Learn guides and services that put the term in context.
- Start in Learn — Understand the concept and the warning signs.
- Move to the Glossary — Decode estimates, specs, and rebate paperwork.
- Book with context — Ask sharper questions during your estimate.
HVAC Terms
14 terms
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HVAC
SEER2
SEER2 (Seasonal Energy Efficiency Ratio 2) is a federal efficiency rating for air conditioners and heat pumps measured under stricter, more real-world test conditions than the old SEER. Higher SEER2 means more cooling per watt. As of January 2023, Austin homes must use systems that meet a SEER2 minimum of 14.3 for split-system AC.
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HVAC
AFUE
AFUE (Annual Fuel Utilization Efficiency) is the percentage of fuel a gas or propane furnace converts into usable heat over a full heating season. An 80% AFUE furnace turns 80 cents of every gas dollar into household heat; the rest goes up the flue. The current federal minimum for non-weatherized gas furnaces is 80% AFUE.
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HVAC
HSPF2
HSPF2 (Heating Seasonal Performance Factor 2) is the federal efficiency rating for the heating side of a heat pump, measured under updated 2023 test conditions. Higher HSPF2 means more heat delivered per kWh. The current federal minimum for heat pumps in Texas is HSPF2 7.5.
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HVAC
BTU & Tonnage
BTU (British Thermal Unit) measures heating or cooling output; one BTU is the heat needed to raise one pound of water 1°F. In HVAC, a ton equals 12,000 BTU per hour of cooling. A 3-ton AC delivers 36,000 BTU/hr. Austin homes typically need 2.5 to 5 tons depending on size, orientation, and insulation.
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HVAC
Manual J Load Calculation
Manual J is the residential load-calculation methodology published by the Air Conditioning Contractors of America (ACCA). It tells you the precise heating and cooling load — in BTU per hour — that a specific home requires, accounting for square footage, insulation, window orientation, duct losses, infiltration, and climate. It's the right way to size an HVAC system.
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HVAC
R-410A and R-454B Refrigerants
R-410A and R-454B are residential AC refrigerants. R-410A has been the standard since 2010 but is being phased down under the AIM Act because of its high global-warming potential (GWP 2,088). New AC and heat pump equipment manufactured in 2025+ uses R-454B (GWP 466) — a lower-GWP replacement that requires updated handling protocols.
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HVAC
MERV Rating
MERV (Minimum Efficiency Reporting Value) is the ASHRAE Standard 52.2 scale for how effectively a filter captures airborne particles. MERV runs 1 to 16 for residential filters, with higher numbers capturing smaller particles. MERV 8 catches dust and pollen; MERV 11-13 catches mold spores and fine particulates; MERV 13 is the sweet spot for Austin homes managing cedar fever.
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HVAC
Heat Pump
A heat pump is HVAC equipment that uses a refrigeration cycle to MOVE heat instead of GENERATING it — pumping heat out of the home in summer (acting as an AC) and into the home in winter (acting as a heater). One heat pump replaces both an AC and a furnace. In Central Texas, where winters are mild, modern heat pumps usually beat gas furnaces on operating cost.
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HVAC
Ductless Mini-Split
A ductless mini-split is a heat pump system that delivers heating and cooling without ductwork. One outdoor compressor connects via small refrigerant lines to one or more wall- or ceiling-mounted indoor head units, each with its own thermostat. Mini-splits excel for additions, garage conversions, ADUs, and stubborn rooms central AC can't satisfy.
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HVAC
Variable-Speed (Inverter) Compressor
A variable-speed (inverter) compressor adjusts its motor speed continuously to match the home's exact cooling or heating load. Instead of cycling fully on and fully off like a single-stage compressor, it runs at 40%, 60%, 90%, or whatever level the moment requires. The result is dramatically better humidity control, quieter operation, and 15-25% better seasonal efficiency.
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HVAC
Capacitor (Start/Run)
An HVAC capacitor is an electrical component that stores energy and releases it to start and run the compressor and condenser fan motor. Start capacitors give a hard kick on startup; run capacitors maintain a steady phase shift while the motor runs. Capacitor failure is the #1 cause of AC no-cool calls in Austin summers — heat and age both kill them.
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HVAC
Short Cycling
Short cycling is when an AC, heat pump, or furnace turns on and off in rapid bursts — typically 2-5 minutes per cycle instead of the normal 10-20 minute run. It wastes energy, wears out components, and leaves the home humid or unevenly heated. Common causes include oversized equipment, dirty coils, restricted airflow, refrigerant problems, and bad thermostats.
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HVAC
Evaporator Coil Corrosion (Formicary)
Formicary corrosion ("ant-nest corrosion") is a microscopic pitting failure of copper evaporator coils caused by organic acids from common household sources — cleaning chemicals, building materials, certain glues, and pesticides. Small tunnels form through the copper wall and the refrigerant leaks. It's a leading cause of evaporator coil failure in years 6-12 of an AC's life.
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HVAC
Refrigerant Leak
A refrigerant leak is loss of refrigerant from the sealed loop that circulates between the indoor evaporator coil and the outdoor condenser. A correctly installed AC should never lose refrigerant. If it does, the leak must be found and sealed — adding refrigerant without finding the leak is a stopgap. Common sources: evaporator coil corrosion, line-set rub-throughs, Schrader valve leaks, and field-brazed joint failures.
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Programs, Codes & Certifications
4 terms
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Multi-trade
Austin Energy Rebate Program
The Austin Energy Rebate Program offers cash incentives to Austin Energy electric customers who upgrade to qualifying high-efficiency HVAC equipment, heat pumps, and insulation/duct improvements. Rebate amounts vary by year and equipment tier. Eligibility usually requires SEER2 ≥ 15.2 and HSPF2 ≥ 8.1 for heat pumps, plus AHRI-matched installation by a participating contractor.
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Multi-trade
IRA HEAR Program
The Home Electrification and Appliance Rebates (HEAR) program is a federal rebate created by Inflation Reduction Act §50122, administered through state energy offices, that pays low- and moderate-income households to replace fossil-fuel and inefficient electric equipment with high-efficiency electric alternatives — including heat pumps, heat pump water heaters, electric stoves, and electrical panel upgrades.
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Multi-trade
EPA 608 Certification
EPA 608 Certification is the federal credential required for anyone who handles refrigerant in stationary HVAC equipment in the United States. It comes in four levels (Type I, II, III, Universal) and is required by EPA Section 608 of the Clean Air Act. Hiring an HVAC company that isn't 608-certified is illegal and is a major red flag for AC work.
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Multi-trade
TDLR Licensed HVAC Contractor
A TDLR Licensed HVAC Contractor is an HVAC company licensed by the Texas Department of Licensing and Regulation under Chapter 1302 of the Texas Occupations Code. The license — TACLA (Class A) or TACLB (Class B) — is required by state law to perform any HVAC work in Texas. Hiring an unlicensed contractor exposes homeowners to permit issues, voided manufacturer warranties, and insurance problems.
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Also see
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