The vocabulary of your HVAC quote.
Plain-English definitions of the terms your technician — and your quote — will use. Bookmark it: when you understand the words, nobody can talk you into the wrong system.
Efficiency & Ratings
- Efficiency & Ratings
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SEER2
Seasonal Energy Efficiency Ratio (version 2) — the 2023+ federal rating for air-conditioning and heat-pump cooling efficiency. Higher means lower summer bills. Louisiana sits in the hot South region, where the minimum for most split-system ACs is 14.3 SEER2.
- Efficiency & Ratings
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HSPF2
Heating Seasonal Performance Factor (version 2) — the 2023+ rating for a heat pump's heating efficiency. A heat pump carries both a SEER2 (cooling) and an HSPF2 (heating) number.
- Efficiency & Ratings
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AFUE
Annual Fuel Utilization Efficiency — how much of a furnace's fuel becomes useful heat. 80% AFUE is standard; 90–96% AFUE condensing furnaces convert more fuel to heat and vent through PVC instead of metal.
- Efficiency & Ratings
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EER2
Energy Efficiency Ratio (version 2) — efficiency measured at a single hot, peak condition rather than across a season. Useful in a place like Baton Rouge where the system spends a lot of time at peak load.
Equipment
- Equipment
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Heat Pump
An air conditioner that can run in reverse to heat as well as cool. It moves heat instead of burning fuel, making it highly efficient — and Baton Rouge's mild winters are nearly ideal for one.
- Equipment
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Geothermal Heat Pump
A ground-source heat pump that exchanges heat with the stable temperature a few feet underground instead of the hot outdoor air. The most efficient HVAC available, but with a higher up-front cost for the buried ground loop.
- Equipment
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Ground Loop
The buried piping a geothermal system circulates fluid through to exchange heat with the earth. It can be horizontal (needs land) or vertical (drilled bores) and often lasts 50+ years.
- Equipment
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Mini-Split
A ductless heat pump with a small outdoor unit and one or more wall- or ceiling-mounted indoor heads. Ideal for additions, garages, and hot bonus rooms because it conditions a space directly with no duct losses.
- Equipment
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Two-Stage Compressor
A compressor that runs at two output levels (roughly 67% and 100%). It spends more time at low stage in mild weather — quieter, more even, and far better at pulling humidity out of the air.
- Equipment
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Variable-Speed ECM
An Electronically Commutated Motor that continuously adjusts blower speed. It uses far less electricity than an older fixed-speed motor and delivers steady airflow and excellent dehumidification.
- Equipment
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Balance Point
The outdoor temperature at which a heat pump's output exactly meets the home's heat loss. Below it, a small amount of backup heat helps out — which in Baton Rouge happens only on rare cold snaps.
- Equipment
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Capacitor
A small, inexpensive electrical component that helps the motors start and run. A failed capacitor is one of the most common — and cheapest — AC repairs, often mistaken for a much bigger problem.
- Equipment
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Compressor
The heart of an AC or heat pump, where refrigerant is pressurized. A failed compressor is expensive, which is why it's a classic 'lean toward replacement' trigger on an older system.
Refrigerant
- Refrigerant
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Refrigerant
The fluid that absorbs and releases heat as it cycles through your system. It isn't 'used up' — if it's low, there's a leak that needs to be found and fixed, not just topped off.
- Refrigerant
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Refrigerant Charge
The precise amount of refrigerant in the sealed system. Both too little and too much cut efficiency by 20% or more, which is why charge must be measured, not eyeballed.
- Refrigerant
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R-22 (Freon)
An older, ozone-depleting refrigerant phased out of production in 2020. Systems that still use it (generally pre-2010) are expensive to repair, so a refrigerant leak often tips toward replacement.
- Refrigerant
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R-410A (Puron)
The HFC refrigerant that replaced R-22. Still common and serviceable, though new production is winding down under the AIM Act in favor of lower-impact A2L refrigerants.
- Refrigerant
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R-454B / R-32 (A2L)
Lower-global-warming 'A2L' (mildly flammable) refrigerants adopted for most 2025+ residential equipment under the AIM Act transition. They require equipment specifically designed for A2L safety.
Comfort & Air Quality
- Comfort & Air Quality
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Relative Humidity
The percentage of moisture in the air relative to what it can hold. Indoors, the comfort and health sweet spot is 40–55%; above 55% a Louisiana home feels sticky and risks mold.
- Comfort & Air Quality
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Latent vs Sensible Heat
Sensible heat is the temperature you feel; latent heat is the moisture in the air. On the Gulf Coast, removing latent heat (humidity) is a huge share of your AC's job — not just lowering the temperature.
- Comfort & Air Quality
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Dehumidifier
A whole-home dehumidifier ties into your ductwork and holds a humidity setpoint independent of cooling. Valuable in efficient or shaded Baton Rouge homes where the AC alone doesn't run enough to dry the air.
- Comfort & Air Quality
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MERV
Minimum Efficiency Reporting Value — an air filter's particle-capture rating (1–16). Most homes do best at MERV 11–13; going higher without the right blower can restrict airflow and hurt the system.
- Comfort & Air Quality
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UV Germicidal Light
An ultraviolet light installed in the air handler to suppress mold and biological growth on the coil — a real benefit in our humidity, though a complement to filtration, not a replacement for it.
- Comfort & Air Quality
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Zoning
A system of motorized dampers and multiple thermostats that sends conditioned air where it's needed, so you can keep an upstairs or bonus room comfortable without overcooling the rest of the house.
Sizing & Airflow
- Sizing & Airflow
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BTU
British Thermal Unit — the basic unit of heating or cooling energy. AC and heating capacity is measured in BTUs per hour. 12,000 BTU/hr of cooling equals one 'ton.'
- Sizing & Airflow
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Ton
A unit of cooling capacity equal to 12,000 BTU/hr. A typical Baton Rouge home uses roughly 2–5 tons, but the right size comes from a load calculation — never a square-footage guess.
- Sizing & Airflow
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Manual J
The industry-standard load calculation that determines exactly how much heating and cooling a specific home needs, room by room. Skipping it is the #1 cause of oversized, humidity-prone systems.
- Sizing & Airflow
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CFM
Cubic Feet per Minute — the volume of air moving through your system or out of a vent. Too little CFM to a far room (like a bonus room) is a common reason a space won't cool.
- Sizing & Airflow
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Static Pressure
The air pressure inside your duct system, like blood pressure for HVAC. High static pressure — from undersized or leaky ducts — strangles airflow and shortens equipment life, even with a brand-new unit.
- Sizing & Airflow
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Short Cycling
When a system turns on and off in quick bursts without completing a full cycle. Often caused by an oversized unit; it wastes energy, wears parts, and — critically in Louisiana — never runs long enough to remove humidity.
Want a tech to walk you through it?
A real Baton Rouge technician will explain anything in this glossary on the phone — no pressure, no sales pitch. Or start with the Learning Center.