Reference
HVAC Glossary
Plain-English definitions for the words you'll hear from any heating, cooling, or indoor-air technician — so you can make confident decisions about your home.
Heating & Cooling
- Heat Pump
- A system that heats and cools by moving heat rather than burning fuel. In winter it pulls heat from outdoor air into your home; in summer it reverses to remove heat.
- Dual-Fuel (Hybrid) System
- A heat pump paired with a gas furnace. The heat pump handles most of the season efficiently, and the furnace takes over on the coldest days.
- Furnace
- A heating appliance that burns gas (or uses electric heat) to warm air, which a blower distributes through ductwork.
- Condenser
- The outdoor unit of an AC or heat pump. It releases heat removed from your home (cooling) or absorbs outdoor heat (heating).
- Evaporator Coil
- The indoor coil where refrigerant absorbs heat from your home's air. Pairing it correctly with the outdoor unit is essential for efficiency.
- Refrigerant
- The fluid that carries heat through an AC or heat pump as it changes between liquid and gas. Different systems use different refrigerants, some of which are being phased out.
- Short-Cycling
- When a system turns on and off too frequently — often a sign of an oversized unit, a dirty filter, or a control fault. It wastes energy and wears out components.
Efficiency & Sizing
- SEER2
- The current efficiency rating for cooling. A higher SEER2 means the system delivers more cooling per unit of electricity over a season.
- AFUE
- Annual Fuel Utilization Efficiency — the percentage of fuel a furnace turns into usable heat. A 95% AFUE furnace converts 95% of its fuel to heat.
- HSPF2
- The current heating-efficiency rating for heat pumps. A higher HSPF2 means more heat delivered per unit of electricity over the heating season.
- Manual J Load Calculation
- The industry-standard method for sizing equipment based on a home's insulation, windows, climate, and layout — not just square footage.
- Variable-Speed (Inverter)
- Equipment that ramps output up and down instead of running only at full blast. It holds steadier temperatures and uses less energy than single-stage gear.
- Ton (of Cooling)
- A unit of cooling capacity equal to 12,000 BTU/hr. Residential systems are commonly 1.5 to 5 tons; the right size comes from a load calculation.
Air Quality
- MERV Rating
- A filter's particle-capture rating. Higher MERV captures smaller particles but can restrict airflow if the system isn't designed for it.
- Whole-Home Humidifier
- Equipment integrated with your HVAC that adds moisture to dry indoor air — useful in our high-desert winters when heating dries the air out.
- Ventilation
- Bringing controlled fresh air into a tight, energy-efficient home to dilute stale indoor air and remove pollutants.
- Air Purification
- Filtration or treatment integrated with your HVAC to reduce allergens, particles, or odors in the air your system already circulates.