Heat pumps work best in mild to moderate climates, especially where a home needs both heating and cooling. Modern cold-climate air-source heat pumps can also perform well in freezing conditions. ENERGY STAR tests qualifying models at 5°F, while ground-source, or geothermal, heat pumps can operate efficiently in almost any climate because they exchange heat with relatively stable underground temperatures.
Which Climate Is Best for Each Type of Heat Pump?
| Climate | Best heat pump choice | Key consideration |
|---|---|---|
| Mild or moderate winters | Standard air-source heat pump | Usually the simplest and most economical application |
| Hot or humid climate | Air-source heat pump | Choose equipment with effective cooling and humidity control |
| Cold winters below freezing | Cold-climate air-source heat pump | Check low-temperature heating capacity and efficiency |
| Very cold winters | Cold-climate air-source, dual-fuel or ground-source system | Backup heating and careful design may be necessary |
| Any climate | Ground-source heat pump | Higher installation cost, but stable year-round performance |
Why Mild Climates Suit Air-Source Heat Pumps
An air-source heat pump transfers heat between the home and outdoor air. In winter, it moves heat indoors. In summer, it reverses the process and removes heat from the building.
As outdoor temperatures fall, less heat is available in the air. An air-source heat pump therefore loses some heating capacity and efficiency in colder weather. That makes mild and moderate climates the easiest conditions for standard air-source systems.
Mild climates are a good fit when:
- Winter temperatures usually stay above or near freezing.
- The home also needs cooling in summer.
- The building has good insulation and limited air leakage.
- Electricity prices make heat-pump operation competitive with gas, oil or electric resistance heating.
- The system is sized for the local heating and cooling loads.
A heat pump can still work well in a cold region, but the equipment and installation need closer attention.
Are Heat Pumps Suitable for Cold Climates?
Yes. Cold-climate heat pumps are suitable for many homes in northern states and other regions with freezing winters.
ENERGY STAR cold-climate air-source heat pumps are tested at 5°F. To earn the cold-climate designation, a split-system model must achieve a coefficient of performance of at least 1.75 at 5°F and retain at least 70% of its heating capacity at 5°F compared with its rated capacity at 47°F.
ENERGY STAR says certified cold-climate air-source heat pumps can continue operating below 5°F. In colder conditions, backup heating can improve reliability and may provide a better overall design.
For a cold climate, look for:
- An ENERGY STAR Cold Climate designation.
- Heating capacity listed at the local design temperature, not only at 47°F.
- A variable-speed or inverter-driven compressor.
- A properly designed defrost cycle.
- Backup heat, such as electric resistance, a gas furnace or another approved system, if the climate requires it.
- An installer with experience designing cold-climate systems.
A standard heat pump intended for a warm region should not automatically be installed in a home that has long periods of subfreezing weather.
How Do Heat Pumps Perform in Hot or Humid Climates?
Air-source heat pumps suit hot climates because the same system provides air conditioning during summer. The heating function can cover cooler winter days without requiring a separate furnace.
Humidity makes sizing more important. An oversized system may reach the thermostat setting quickly but run for too little time to remove enough moisture from the indoor air. Equipment selection should account for both sensible cooling and humidity removal.
ENERGY STAR notes that modern heat pumps can dehumidify more effectively than standard central air conditioners in some applications.
For hot and humid regions, prioritize:
- Proper sizing instead of choosing the largest available unit.
- Variable-speed operation where appropriate.
- A design that accounts for latent humidity loads.
- Well-sealed ducts and adequate airflow.
- An installer familiar with local humidity conditions.
Is a Ground-Source Heat Pump Better for Extreme Climates?
Ground-source heat pumps are the most climate-independent option. They exchange heat with the ground instead of relying directly on outdoor air. Underground temperatures change less than air temperatures, which helps geothermal systems maintain consistent performance in hot summers and cold winters.
The U.S. Department of Energy says geothermal heat pumps can be installed in all climates, including urban and rural environments. They may be especially suitable when a property has enough land or drilling access and the owner expects to remain in the building for many years.
The main drawback is installation cost. The ground loop may require horizontal excavation, vertical drilling or a suitable water source. Permitting and specialist design may also be necessary.
The Climate Is Not the Only Factor That Matters
Two homes in the same climate can have very different heat-pump results. The main factors are:
Home insulation and air sealing A poorly insulated home loses heat faster and needs more heating capacity.
System sizing The heat pump should be selected using the home's heating and cooling load, local outdoor design temperatures and the equipment's actual low-temperature performance.
Ductwork or indoor distribution Leaky, undersized or poorly insulated ducts can reduce comfort and efficiency.
Electricity and fuel prices A heat pump may reduce energy use without reducing total operating cost if electricity is expensive compared with gas or heating oil.
Backup heating requirements Cold-climate installations may use supplemental electric heat, a furnace or another heating source during extreme weather.
Installer experience Incorrect sizing, poor airflow, unsuitable controls or inadequate commissioning can reduce performance in any climate.
The Department of Energy recommends weatherizing homes, particularly older properties, before installing an air-source heat pump. Improvements to the building envelope can increase comfort and reduce energy costs.
Bottom Line
- Best climate for a standard air-source heat pump: Mild to moderate climate with a need for both heating and cooling.
- Best choice for a cold climate: An ENERGY STAR Cold Climate air-source heat pump, often paired with carefully selected backup heat.
- Best option for consistent performance in extreme climates: A ground-source or geothermal heat pump, if the higher installation cost is justified.
- Best approach in a humid climate: A correctly sized, variable-capacity system designed for temperature control and moisture removal.
The best system depends on more than the climate label. Local winter design temperature, summer humidity, the building envelope, utility rates and installation quality all affect the result.