The terms, in plain English.
18 HVAC and electrical terms defined without the jargon — each links to the guide that goes deeper.
Heating & Cooling
- SEER2
- The current efficiency rating for air conditioners and heat pumps — how much cooling you get per unit of electricity over a season. Higher SEER2 means lower running cost. It replaced the older SEER scale in 2023. Read: What does AC replacement cost in Fort Bend County? →
- HSPF2
- The heating-season efficiency rating for a heat pump — the counterpart to SEER2 for cooling. Higher HSPF2 means the heat pump delivers more heat per unit of electricity.
- Tonnage
- A measure of an AC or heat pump's cooling capacity (one ton ≈ 12,000 BTU/hr). Sizing is set by a load calculation, not square footage alone — an oversized unit short-cycles and doesn't dehumidify.
- Heat pump
- A system that moves heat rather than making it, so it can both cool and heat by reversing its refrigerant cycle. Well suited to Fort Bend's mild winters and long cooling season. Read: How does a heat pump work? →
- Short-cycling
- When a system turns on and off in quick bursts instead of running steady cycles. It's often a sign of oversizing, low refrigerant or an airflow problem, and it leaves a home cool but humid. Read: Why is my home humid even with the AC running? →
- Evaporator coil
- The indoor coil where refrigerant absorbs heat and moisture from your home's air. It's cold and damp when the AC runs — which is why it's a target for mold and a UV light. Read: What do UV lights do in an HVAC system? →
- Condenser
- The outdoor unit that releases the heat pulled from your home. Keeping it clear of leaves and debris helps it shed heat and run efficiently.
- Capacitor
- A small component that gives the AC's motors the jolt they need to start and run. A failed capacitor is a common, routine repair — often the reason an outdoor fan won't spin. Read: Why is my AC running but not cooling? →
- Refrigerant (R-410A / R-22)
- The fluid that carries heat through the system. R-22 is phased out and costly, which pushes older units toward replacement; R-410A and newer refrigerants are standard on current systems. Read: Should I repair or replace my air conditioner? →
- Ductless mini-split
- A heat pump that conditions a zone directly through a wall or ceiling head, with no ductwork — ideal for additions, garages and rooms central air can't reach. Read: What is a ductless mini-split? →
Electrical
- Circuit breaker
- A safety switch that cuts power when a circuit draws too much current. A breaker that trips repeatedly is signalling an overload, short or ground fault — not asking to be reset. Read: Why does my breaker keep tripping? →
- GFCI
- Ground-fault circuit interrupter — shock protection that cuts power when current leaks to ground. Required near water: kitchens, baths, garages, outdoors. Read: What are GFCI and AFCI outlets? →
- AFCI
- Arc-fault circuit interrupter — fire protection that trips when it detects the dangerous sparking of a damaged wire or loose connection. Required in most living areas by current code. Read: What are GFCI and AFCI outlets? →
- Electrical panel (service)
- The box that distributes power to your home's circuits, rated in amps (e.g. 100A, 200A). Adding major loads like central AC or an EV charger can require a larger panel. Read: Do I need an electrical panel upgrade? →
- Whole-home surge protection
- A device at the panel that shields the entire electrical system — including hard-wired HVAC and appliances — from the voltage spikes a plug-in strip can't cover. Read: Does my home need whole-home surge protection? →
Indoor Air Quality
- MERV
- A filter's particle-capture rating (roughly 1–16). MERV 8–13 suits most homes; too high a MERV for the system can choke airflow. Read: What do MERV filter ratings mean? →
- Duct sealing / Aeroseal
- Closing the leaks where conditioned air escapes the ductwork — often into a hot attic. Aeroseal is an interior sealing method. Sealing restores airflow to far rooms and cuts waste. Read: What does duct sealing do? →
- Whole-home dehumidifier
- Equipment added to the HVAC system that controls humidity independently of temperature — useful when Gulf-Coast humidity leaves a home clammy even with the AC keeping up. Read: Why is my home humid even with the AC running? →