Clear, plain-English definitions—with why each term matters for your decision. Search or jump by letter. Each term has a shareable link.
Certified pairing of outdoor unit, indoor unit, and coil with a rating certificate.
Required for many rebates and proofs of performance. Ensures the exact combo you buy delivers the advertised efficiency and capacity.
The indoor unit that moves air across the coil and through ducts.
Contains the blower, heat/cool coil, filter slot, and controls. For ductless, the “air handler” is the wall/ceiling head.
Electric resistance elements inside the air handler for rare extremes and defrost support.
Often sized modestly (e.g., 5–10 kW) to avoid bill spikes while providing safety margin.
Outdoor temperature where heat pump capacity equals the home’s heat loss.
Above it, the heat pump carries the load; below it, supplemental heat (strips/furnace) is needed.
Heating/cooling power expressed as British Thermal Units per hour.
1 ton = 12,000 BTU/h. Compare equipment capacity to your home’s design load.
Cubic feet per minute—how much air your system moves.
Correct CFM is essential for comfort, capacity, and coil health.
Variable-speed models engineered to maintain capacity and useful COP at low temperatures (e.g., 5°F, −5°F).
Often includes enhanced vapor injection or optimized compressors/controls for the cold.
Verification and tuning after install: airflow, refrigerant charge, controls, and safety checks.
Good commissioning locks in efficiency, comfort, and longevity.
Water produced when moist air is cooled below its dew point at the coil.
Requires proper drains, traps, and sometimes pumps to prevent leaks.
Heat delivered ÷ electric energy used (e.g., COP 2.5 = 250% efficient).
Varies with outdoor temperature and model class.
Short reverse cycle to melt frost on the outdoor coil; airflow/heat shift briefly.
Steam plumes are normal during defrost—this isn’t “smoke.”
Local cold-weather benchmark used for sizing; 99% of winter hours are warmer.
We size to DB99—not the record low—to balance comfort and ROI.
Heat pump + furnace. HP runs most hours; furnace takes rare deep-cold via lockout.
Optimized with an economic lockout temperature based on your rates and model COP.
Balanced ventilation with energy recovery (moisture with ERV; sensible heat with HRV).
Delivers fresh air with minimal energy penalty and better humidity control.
Moves heat between indoors and outdoors using refrigerant—heats in winter, cools in summer.
Efficiency depends on outdoor temperature and model class.
Water heater using a small heat pump to move heat into the tank.
2–3× more efficient than resistance water heaters; may cool/dehumidify the room it’s in.
Seasonal heating efficiency rating under updated test procedures.
Useful, but pair with capacity at low temps and COP for full context.
Outdoor temp where HP cost per MMBtu equals your fuel system; below it, fuel may be cheaper.
Set as the switchover temperature in dual-fuel controls.
Standard method to calculate your home’s heating and cooling loads.
Considers insulation, windows, orientation, infiltration, and more.
Selects specific equipment to meet the Manual J load across temperatures.
Uses manufacturer submittals, not just nameplate tonnage.
Duct design to deliver correct airflow (CFM) at acceptable static pressure.
Elbows, trunk sizes, and returns are sized—not guessed.
Register/diffuser selection and placement.
Controls air throw and mixing for even room temperatures.
Filter particle capture rating (higher = finer).
Balance filtration with airflow needs; check pressure drop.
O/B wires control the reversing valve. “Emergency Heat” runs furnace/strips and locks out the HP.
Correct thermostat configuration is crucial for dual-fuel and strip logic.
Tubing connecting indoor and outdoor units; length and size affect capacity and charge.
Manufacturers specify max length and vertical rise; long runs may need adjustments.
Seasonal cooling efficiency rating (updated test).
Good for summer bills; for winter, prioritize heating metrics and low-temp capacity.
Your target indoor temperature (e.g., 70°F heat / 75°F cool).
Heat pumps like steady setpoints—less swing than furnaces.
Frequent on/off due to oversizing or airflow problems.
Reduces comfort and efficiency; stresses components.
Resistance to airflow in ducts, measured in inches water column (in. w.c.).
Too high → noise, poor airflow, efficiency loss.
Refrigerant diagnostics used to verify charge and system health.
Measured during commissioning and service; must align with manufacturer targets.
Electric prices vary by hour/season; off-peak is cheaper.
Shift heating hours and water-heating to save more.
1 ton = 12,000 BTU/h.
Typical whole-home systems are 2–4 tons depending on climate and envelope.
Control setting that disables HP below a chosen temperature or prevents strips above it.
Used to implement economic or thermal switchover logic.
Compressor and fan speeds modulate to match load instead of cycling on/off.
Improves comfort, efficiency, and cold-weather capacity retention.
Multi-zone inverter systems that vary refrigerant flow to many indoor units.
Common in larger homes and light commercial; highly flexible zoning.
Air sealing and insulation upgrades that reduce heat loss/gain.
Lowers your load, improves balance point, and can reduce required tonnage.
Space around the outdoor unit required for airflow and service.
Includes distance to walls, snow stand height, and coil breathing room.