Heat Pump Install Glossary

Plain-English explainers for the technical terms, rebates, regulations, and acronyms that show up when you shop for Heat Pump Install systems and services. Each entry links the underlying source, lists the numbers that matter, and points to related concepts.

AHRI Certified / Matched System
The rated efficiency only holds if the indoor and outdoor units are the specific AHRI-certified pair — and rebates require that number.
Air-Source Heat Pump (ASHP)
One outdoor unit that both heats and cools by moving heat instead of burning fuel — the system a heat-pump install centers on.
Backup Heat (Auxiliary / Emergency Heat)
The supplemental heat that kicks in below the balance point — usually electric strips, and far costlier to run than the heat pump itself.
Balance Point
The outdoor temperature where a heat pump can just keep up with the home's heat loss — below it, backup heat switches on.
Cold-Climate Heat Pump (ccASHP)
A heat pump engineered to hold most of its capacity at 5°F — what makes a heat pump viable as the only heat source in cold winters.
COP (Coefficient of Performance)
How many units of heat a heat pump delivers per unit of electricity — the single number that explains why a heat pump beats a furnace.
Defrost Cycle
The brief reversal that melts frost off the outdoor coil in cold, damp weather — normal, but smart controls keep it from wasting energy.
Dual-Fuel (Hybrid Heat) System
A heat pump paired with a gas furnace — the heat pump handles mild weather, the furnace takes over when it's coldest.
Geothermal (Ground-Source) Heat Pump
A heat pump that exchanges heat with the stable-temperature earth instead of outdoor air — the most efficient, and most expensive, option.
HSPF2 (Heating Seasonal Performance Factor 2)
The heating-efficiency score of a heat pump — the rating that matters most because a heat pump is your primary heat source.
Manual J Load Calculation
The room-by-room heat-loss/heat-gain math that sizes a heat pump — the step that separates a right-sized install from a guess.
SEER2 (Seasonal Energy Efficiency Ratio 2)
The cooling-efficiency score of a heat pump, on the 2023 M1 test scale — lower-looking than old SEER for the same equipment.
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