Glossary · Heating, cooling & ventilation

Air-source heat pump (ASHP)

Also called: air-source heat pumps · air-to-air heat pump

A heat pump that takes heat from outdoor air in winter and releases heat outdoors in summer, using an outdoor unit with a fan.

What it means

An outdoor unit with a fan and compressor connects by refrigerant lines to an indoor coil in your ductwork or to wall-mounted heads (see ductless mini-split). Its efficiency and capacity drop as outdoor temperatures fall, and it runs short defrost cycles in cold, damp weather. Cold-climate models keep heating efficiently well below freezing.

Why it matters in an audit

Choosing the right model for your climate, sizing it with a load calculation and planning auxiliary heat decide how much it will actually save.

Typical numbers

Reference values with their sources. Your auditor’s report gives the figure for your own house.

What	Value	Source
Efficiency, NRCan	COP typically 2.0–5.4 at 46°F (8°C); 1.1–3.7 at 18°F (−8°C)	natural-resources.canada.ca ↗
Low-temperature limit, NRCan	Newer models' minimum operating temperatures range from 5°F to −13°F (−15°C to −25°C)	natural-resources.canada.ca ↗
US federal minimum (2023)	Split: SEER2 14.3, HSPF2 7.5; single-package: SEER2 13.4, HSPF2 6.7	www1.eere.energy.gov ↗
ENERGY STAR (heat pump spec 6.2, rev. Feb 2026)	Split: SEER2 ≥ 15.2, EER2 ≥ 11.0, HSPF2 ≥ 7.8; single-package: SEER2 ≥ 15.2, EER2 ≥ 10.0, HSPF2 ≥ 7.2	energystar.gov ↗

Sources

Learn more here

Heat pump comparison guide →

Related terms

Heat pump An electric system that moves heat instead of making it: out of the house in summer and into it in winter, using a refrigerant loop.
Cold-climate heat pump (ccASHP) An air-source heat pump built to keep heating efficiently in deep cold, usually verified by ENERGY STAR Cold Climate or the NEEP list.
HSPF / HSPF2 A heat pump's heating efficiency averaged over a whole heating season; higher is better, and HSPF2 numbers can't be compared directly with older HSPF.
SEER / SEER2 An air conditioner's or heat pump's cooling efficiency averaged over a whole cooling season; higher is better.
COP (coefficient of performance) Heat delivered divided by electricity used at a given moment; a COP of 3 means three units of heat for each unit of electricity.
Balance point The outdoor temperature where something changes: below the thermal balance point a heat pump needs help; below the economic one, fuel is cheaper.
Auxiliary / backup heat A second heat source — electric elements or a furnace — that helps a heat pump in very cold weather or during defrost.
Ductless mini-split An air-source heat pump with wall- or ceiling-mounted indoor heads connected by refrigerant lines, needing no ductwork.
Ducted heat pump A heat pump that heats and cools through ductwork, like central air conditioning, either on its own or paired with a furnace.
Defrost cycle (heat pumps and HRVs) A short, automatic cycle that melts frost off a heat pump's outdoor coil or an HRV's core in freezing weather; it's a normal part of winter operation.
Refrigerant (R-454B, R-32, R-410A) The fluid a heat pump or air conditioner pumps around to move heat; newer systems use R-454B or R-32 instead of the older R-410A.
Seasonal COP A heat pump's average heat output per unit of electricity over a whole heating season, including defrost and backup heat, instead of at one temperature.

← Every term, A to Z