The HVAC terms KC homeowners actually ask about.
33 plain-English definitions — sourced from EnergyStar, the Department of Energy, ASHRAE, and manufacturer documentation, never marketing copy. Cross-linked so you can follow related concepts.
Showing 33 of 33 terms.
A
AFUE (Annual Fuel Utilization Efficiency)
The percentage of fuel a furnace converts into usable heat over a typical year. An 80% AFUE furnace turns 80 cents of every $1 of gas into heat; the other 20 cents leaves through the flue.
Read full definitionAir conditioner (central AC)
The cooling side of a typical split-system HVAC. The outdoor unit (condenser) and indoor coil (evaporator) move heat from inside your home to outside using refrigerant.
Read full definitionAir handler
The indoor blower + evaporator coil assembly that moves conditioned air through your ducts. In a furnace-paired system the air handler is the blower built into the furnace; in a heat-pump-only system it's a standalone box (no combustion).
Read full definitionB
Blower (motor)
The fan that pushes conditioned air through your ductwork. Variable-speed (ECM) blowers run quieter, more efficient, and at multiple speeds to match demand; older PSC blowers run on/off at one speed.
Read full definitionBTU (British Thermal Unit)
The unit of heat used to size HVAC equipment. One BTU is the heat required to raise one pound of water by one degree Fahrenheit. A typical 2,000 sq ft KC home needs around 24,000–36,000 BTU/h of cooling and 40,000–80,000 BTU/h of heating, depending on insulation, windows, and orientation.
Read full definitionC
Compressor
The pump inside the outdoor condenser that moves refrigerant between the indoor and outdoor coils. When the compressor fails, the system can't cool — and a new compressor on an older unit is often the moment the 5,000 rule (repair cost × age) tips toward replacement.
Read full definitionCondenser (outdoor unit)
The big metal box outside your house. Contains the compressor, the outdoor coil, and a fan. In cooling mode, it dumps heat from inside your home to outside. The condenser is what people usually mean when they say 'the AC unit.'
Read full definitionD
Dual-fuel (hybrid system)
A heat pump paired with a gas furnace. The heat pump handles heating down to a 'switchover' outdoor temperature (typically 30–40°F); below that the gas furnace takes over. Common in KC where winters get below the efficient operating range for most heat pumps.
Read full definitionDuctwork
The network of sheet-metal (or flexible) channels that carries conditioned air from your air handler to every room and returns cooler/warmer air back. Ductwork sized + sealed correctly is the difference between a high-efficiency system that performs and one that doesn't.
Read full definitionE
ERV (Energy Recovery Ventilator)
A whole-house ventilator that swaps stale indoor air for fresh outdoor air while transferring most of the heat AND moisture between the two streams. ERVs are appropriate for hot/humid climates and for homes that want fresh air without dumping conditioned energy.
Read full definitionEvaporator coil
The indoor coil inside your air handler or above your furnace. Cold refrigerant flows through it; your blower pushes warm indoor air across it; the refrigerant absorbs the heat and your air comes out cooler.
Read full definitionH
Heat pump
An air-conditioning system that can run in reverse to heat your home in winter. In cooling mode it works identically to a central AC. In heating mode it moves heat from outdoor air into your home — even at 20°F outside there's still heat in the air to extract.
Read full definitionHigh-efficiency (equipment)
Equipment that exceeds the federal minimum efficiency by a meaningful margin: typically 16+ SEER2 cooling, 95%+ AFUE heating, or 9+ HSPF2 heat pump. Higher upfront cost; lower run cost; usually quieter and more comfortable; often qualifies for federal tax credits and utility rebates.
Read full definitionHRV (Heat Recovery Ventilator)
Like an ERV but transfers only heat (not moisture) between incoming and outgoing air streams. Appropriate for cold/dry climates; usually paired with a separate humidifier.
Read full definitionHSPF2 (Heating Seasonal Performance Factor)
The efficiency rating for heat pumps in heating mode — higher is more efficient. Like SEER2, HSPF2 replaced HSPF in 2023 with stricter test conditions, so HSPF2 numbers are ~15% lower than the old HSPF on the same unit.
Read full definitionI
Indoor air quality (IAQ)
The cleanliness and health-friendliness of the air inside your home — particles (dust, pollen, smoke), allergens, humidity, CO2, and VOCs. IAQ equipment includes higher-MERV filtration, UV germicidal lights, whole-house dehumidifiers, ERVs, and HRVs.
Read full definitionIRA tax credit (25C / 25D)
Federal tax credits introduced by the Inflation Reduction Act for energy-efficient home equipment. The 25C Energy Efficient Home Improvement Credit covers a percentage of qualifying HVAC upgrades up to annual caps. [verify: 2026 cap amounts — confirm current IRS publication before quoting numbers to a customer.]
Read full definitionM
Manual D (duct design)
The engineering math that sizes and routes ductwork to match the system load (Manual J). Manual D verifies the ducts can actually move the air the system is rated for. Skipped duct design is one of the most common reasons a new high-efficiency unit underperforms.
Read full definitionMERV (Minimum Efficiency Reporting Value)
A 1–20 rating for how well an air filter captures particles. MERV 8 is a typical 1-inch filter — catches dust and pollen. MERV 11–13 captures finer particles (smoke, mold spores, some bacteria) and is appropriate for most residential systems. MERV 16+ is hospital/HEPA territory and usually requires a media cabinet, not a 1-inch slot.
Read full definitionR
R-410A refrigerant
The refrigerant used in most residential AC + heat pump systems sold from 2010 through early 2025. R-410A is being phased out for new equipment because of its high global warming potential.
Read full definitionR-454B refrigerant
The refrigerant replacing R-410A in new residential AC + heat pump systems from 2025 onward. R-454B has roughly one-fifth the global warming potential of R-410A and similar cooling performance. It is mildly flammable (A2L class) which means new systems use modified components but install the same way.
Read full definitionS
SEER2
The current efficiency rating for residential air conditioners and heat pumps in cooling mode — higher is more efficient. SEER2 replaced the older SEER rating in 2023; a SEER2 number is ~5% lower than the old SEER on the same unit because the test conditions are stricter.
Read full definitionSingle-stage
Equipment that runs at one speed: full output when on, off when not. The most basic and lowest-cost tier. Works fine but produces bigger temperature swings and higher humidity than two-stage or variable-speed equipment.
Read full definitionSmart thermostat
A thermostat that learns your schedule, supports remote control + setbacks, and reports run-time + efficiency data. Pairs well with variable-speed equipment that can take advantage of finer control.
Read full definitionStatic pressure
The resistance air encounters moving through your ductwork + filter + coil — measured in inches of water column. High static pressure means the blower has to work harder than it should, which kills efficiency, increases noise, and shortens equipment life. Often caused by undersized ducts, a too-restrictive filter, or a dirty coil.
Read full definitionT
Ton (of cooling)
The capacity unit for air conditioners and heat pumps in cooling mode. One ton = 12,000 BTU/h. A 3-ton AC delivers 36,000 BTU/h of cooling.
Read full definitionTwo-stage
Equipment that runs at two output levels — typically a low stage around 65% of capacity for mild weather and a high stage at 100% for the hottest or coldest days. Better humidity control and quieter than single-stage; less expensive than variable-speed.
Read full definitionW
Whole-house dehumidifier
A standalone unit that removes moisture from your home's air, independent of the AC's cooling cycle. Important in KC summers when the AC keeps the temperature comfortable but humidity stays high (often because the AC is oversized and short-cycles instead of running long enough to wring water out).
Read full definitionWhole-house humidifier
An add-on that injects moisture into the supply air to keep indoor humidity in the 35–50% comfortable range during dry winter months. KC winters routinely drop indoor humidity below 20% without supplementation, which dries skin and irritates respiratory systems.
Read full definition