An air-source heat pump transfers heat between outdoor air and the home. It can provide both heating and cooling, and it is the basic technology behind central ducted heat pumps and ductless mini-splits.
How an Air-Source Heat Pump Works
In heating mode, refrigerant absorbs heat from outdoor air, the compressor raises its temperature and pressure, and the indoor coil releases that heat into the home. In cooling mode, the cycle reverses and removes heat from indoors.
- Outdoor coil: exchanges heat with outdoor air.
- Compressor: circulates and compresses refrigerant.
- Indoor coil: exchanges heat with indoor air.
- Expansion device: controls refrigerant pressure and flow.
- Reversing valve: changes the direction of the refrigeration cycle.
- Blower or indoor fan: delivers conditioned air.
Central vs. Ductless Air-Source Heat Pumps
Central ducted
Uses an air handler or compatible furnace blower and a duct system to heat and cool the home.
Ductless mini-split
Uses one or more indoor units without a conventional central duct system.
Do Air-Source Heat Pumps Work in Cold Climates?
They can. The relevant question is how much heating capacity and efficiency the exact model retains as outdoor temperature falls. Cold-climate equipment is designed to maintain stronger low-temperature performance than basic mild-climate systems.
For Kachina Village and Flagstaff-area homes, equipment selection should be based on the home’s heating load, low-temperature output, backup heat, airflow, electrical capacity, and outdoor-unit location.
Why Heat Pumps Can Use Electricity Efficiently
Electric resistance heat converts electricity directly into heat. A heat pump uses electricity to move heat, so it can deliver more heat energy to the home than the electrical energy it consumes under many operating conditions.
Actual efficiency varies with outdoor temperature, equipment, controls, airflow, and system design. A heat pump should not be described with one fixed efficiency number for every winter condition.
What Changes as Outdoor Temperature Falls?
- The home usually needs more heat.
- Heat-pump capacity may change.
- Heat-pump efficiency may change.
- Defrost cycles may occur more often under some conditions.
- Backup heat may be required depending on the design.
That relationship is why sizing and equipment data matter more than generic claims about a heat pump’s minimum operating temperature.
Heat pump sizing and Manual J →
What Is Defrost?
In heating mode, moisture can freeze on the outdoor coil. The heat pump periodically enters defrost to melt that frost. Steam, water, or temporary changes in sound can be normal during this process.
Persistent heavy ice that does not clear is different and may indicate a service problem or poor outdoor-unit conditions.
Backup Heat Options
Air-source heat pumps can be paired with several backup strategies depending on the home and system.
- Electric auxiliary heat: commonly integrated with central air handlers.
- Propane or gas furnace: used in a dual-fuel arrangement.
- Existing supplemental heat: may remain for resilience in some homes.
For furnace backup, see dual-fuel heat pumps.
Air-Source Heat Pump vs. Furnace
| Feature | Air-source heat pump | Furnace |
|---|---|---|
| Heating method | Transfers heat | Generates heat through combustion or resistance |
| Cooling | Yes | No, unless paired with separate cooling equipment |
| Fuel | Electricity | Propane, gas, or electricity depending on furnace |
| Cold-weather design | Depends on equipment and backup strategy | Depends on furnace capacity and fuel supply |
For the local fuel comparison, see heat pump vs. propane.
Air-Source vs. Ground-Source and Water-Source Heat Pumps
Air-source systems exchange heat with outdoor air. Ground-source systems exchange heat with the ground through buried loops. Water-source systems use a water loop or suitable water source. These are different system categories with different site, design, and installation requirements.
For background, see geothermal heat pumps and water-source heat pumps.
What Affects Air-Source Heat Pump Installation Cost?
- System type and capacity.
- Low-temperature performance category.
- Ductwork or number of ductless zones.
- Electrical work.
- Backup heat.
- Outdoor mounting and snow clearance.
- Controls and thermostat setup.
- Refrigerant-line routing.
- Removal of existing equipment.
Common Air-Source Heat Pump Mistakes
- Sizing from square footage alone.
- Ignoring low-temperature capacity.
- Assuming existing ducts are automatically suitable.
- Using a poor outdoor location for snow and drainage.
- Failing to plan backup heat.
- Ignoring electrical capacity until after equipment selection.
- Assuming a larger unit automatically improves winter comfort.
Air-Source Heat Pump FAQs
Is a mini-split an air-source heat pump?
Yes. A ductless mini-split exchanges heat with outdoor air, so it is a type of air-source heat pump.
Is a central heat pump an air-source heat pump?
Most conventional residential central heat pumps are air-source systems unless the project specifically uses ground or water loops.
Does an air-source heat pump need backup heat?
Not every system needs the same backup strategy. The answer depends on the home’s heating load, the selected equipment’s cold-weather output, electrical capacity, and the design goals.