How Heat Pumps Work and When to Consider One

Heat pumps are one of the most energy-efficient ways to heat and cool a home. Unlike traditional furnaces and air conditioners that generate heat through combustion or electric resistance, heat pumps move heat from one place to another. This fundamental difference makes them remarkably efficient — in many cases delivering three to four units of heating or cooling for every unit of electricity consumed.

The Basic Principle

A heat pump does not create heat. It transfers it. In cooling mode, it extracts heat from inside your home and releases it outdoors, exactly like a central air conditioner. In heating mode, it reverses the process, absorbing heat from the outdoor air (even in cold weather) and transferring it inside.

This heat transfer is possible because refrigerant circulating through the system has a very low boiling point. Even when outdoor temperatures drop below freezing, the refrigerant can absorb thermal energy from the air. A compressor then raises the temperature and pressure of the refrigerant, making it hot enough to warm your indoor air.

Key Components

Compressor

The heart of the system, the compressor pressurizes the refrigerant, raising its temperature. Modern variable-speed compressors can modulate their output to match demand precisely, improving efficiency and comfort.

Reversing Valve

This component distinguishes a heat pump from a standard air conditioner. The reversing valve changes the direction of refrigerant flow, switching between heating and cooling modes.

Expansion Valve

The expansion valve reduces the pressure of the refrigerant, causing it to cool rapidly. This cold refrigerant then absorbs heat from the outdoor air (heating mode) or indoor air (cooling mode).

Types of Heat Pumps

Air-Source Heat Pumps

The most common type, transferring heat between your home and the outside air. Advances in compressor technology have significantly improved cold-weather performance, with some models maintaining full heating capacity down to negative 5 degrees Fahrenheit.

Best for: Most residential applications, especially in climates with moderate to mild winters.

Ground-Source (Geothermal) Heat Pumps

Geothermal systems use the stable temperature of the earth below the frost line as their heat source and sink. Because ground temperatures remain relatively constant year-round, these systems are extremely efficient regardless of outdoor weather.

Best for: New construction or homes with adequate land for ground loops. Homeowners planning to stay long-term.

Ductless Mini-Split Heat Pumps

These combine an outdoor unit with one or more indoor air handlers, requiring no ductwork. Each indoor unit serves a specific zone with independent temperature control.

Best for: Homes without existing ductwork, room additions, or supplemental heating and cooling.

Efficiency Ratings

SEER2 (Seasonal Energy Efficiency Ratio) — Measures cooling efficiency. Modern heat pumps range from 14 to over 25 SEER.
HSPF2 (Heating Seasonal Performance Factor) — Measures heating efficiency. Current models range from 8 to over 13 HSPF.

When a Heat Pump Makes Sense

Replacing both your furnace and AC simultaneously
Reducing fossil fuel use — Heat pumps run on electricity, compatible with solar panels
Moderate climate — Where winter temperatures rarely drop below 20–30 degrees Fahrenheit
Zone control — Ductless models allow independent room-by-room control

When a Heat Pump May Not Be the Best Choice

Very cold climates without access to cold-climate models
Homes with aging ductwork needing significant upgrades
Areas with very high electricity rates compared to natural gas
Budget constraints — upfront costs can be higher than a basic furnace replacement

With continuing improvements in cold-weather performance and growing incentives for electrification, heat pumps are an increasingly attractive option for homeowners in nearly every climate. To get the most out of a heat pump, pair it with a compatible smart thermostat. The Ecobee SmartThermostat Premium is designed to work with heat pump systems including auxiliary heat staging — preventing over-reliance on expensive backup resistance heat when outdoor temperatures drop.