What Does a Heat Pump Do?

What Does a Heat Pump Do


A heat pump moves heat from one location to another, instead of creating warmer or cooler air like other HVAC systems. According to, it may use about 50% less electricity than a furnace or baseboard heater. If the temperature in your region rarely drops below freezing, a heat pump is a reliable option.

Heat pumps have become more popular in the United States. Sales of ground-source heat pumps doubled from 2010 to 2020, according to the International Energy Agency. There were 2.3 million air-to-air heat pumps shipped in 2015; by 2020, that number jumped to 2.4 million. So, what does a heat pump do? We will explain in more detail below.


How a Heat Pump Works

A heat pump transfers heat using electricity, much like a refrigerator does. It can move heat into your home, even if it’s relatively cool outside. However, the unit is effective in summer too, as it can reverse to move heat from inside your house to the outdoor air.

As the unit pulls heat from the outside, air is compressed and exchanged to increase the temperature of a refrigerant. Heated air is then directed into the home. A heat pump works on its own, using electricity, and does not require an air conditioner or furnace.


Heat Pump Parts

The most important parts of a heat pump include:

  • Compressor: Traditional compressors only work at one speed and are therefore inefficient. Heat pumps can use two-speed compressors to adjust to the required capacity based on outdoor temperature (operating costs and compressor wear can be reduced). Two-speed heat pumps are suited for zone control systems in larger homes.
    • A scroll compressor works by compressing refrigerant to warm the air. Variable-speed motors, located on inside or outside fans, control airflow into the home at a comfortable velocity, which reduces noise, minimizes drafts, and improves efficiency. You can therefore save on your electrical bills compared to a traditional HVAC system.
  • Evaporator/Condenser: A heat-exchanging coil that transfers heat between refrigerant flowing through the tubes and the air around them. In a heat pump, this coil can be used as an evaporator or condenser, depending on the direction the refrigerant is flowing.
  • Accumulator: Collects excess refrigerant, in liquid state, that hasn’t evaporated and boils it off into a vapor. The gaseous refrigerant is then returned to the compressor, which could be damaged if any liquid gets into it.
  • Electronically Commutated Blower Motor (ECM): Efficient brushless DC motors that work at a range of speeds. Used with most two-stage or multi-stage heat pumps, these draw less power than motors on standard heat pumps.
  • Reversing Valve: Automatically changes the direction of refrigerant flow based on input from a thermostat or defrost control. It switches the pump from cooling to heating modes, or vice versa.
  • Expansion Device: Controls refrigerant flow from the condenser to evaporator and reduces its pressure and temperature to extract heat. In more advanced, high-efficiency heat pumps, a thermostatic expansion valve is used.
  • Electronic Control: Monitors and controls system operation, including speed, temperature, and defrost mode, and provides diagnostics. Likewise, a thermostat controls and monitors temperature to manage comfort levels.
  • Defrost System: Frost can build up on an air-to-air heat pump’s evaporator coil if the outside air temperature drops below 32℉. A defrosting system directs compressed heat to the outdoor coil, melting ice, without affecting indoor air temperature.
  • Desuperheater: Found in some high-efficiency heat pumps, it recovers waste heat during the cooling process to heat up water. Compared to a standard electric water heater, a desuperheater-equipped heat pump heats water up to 3x more efficiently.


Types of Heat Pumps

An air-source heat pump has a main unit outside the home, delivering extracted heat via an internal piping system. A ductless, or mini-split heat pump, does not require any ductwork and is suited for homes that do not have it. Another type is a reverse cycle chiller, which heats water instead of air and directs it through a radiant floor heating system.

Geothermal heat pumps transfer heat from a ground or water source, where temperatures are relatively constant year-round. A geothermal system suits various types of homes and is effective at controlling humidity as well. However, suitability depends on lot-size (space is needed for underground pipes), the landscape surrounding it, and subsoil properties.

When It Gets Too Cold

Ground-source heat pumps are best for areas with colder winters. But with heat pumps in general, heat transfer becomes more difficult if outdoor temperatures drop low enough. While heat pumps have become more versatile, you may want to consider combining one with a furnace. A dual-fuel or hybrid system can improve efficiency and reduce electricity use at low temperatures.

Contact Us to Have Your Heat Pump Questions Answered

Hays Heating, Cooling & Plumbing can install, repair, and maintain your heat pump system with a focus on quality and dependability. We have served clients throughout the Phoenix Valley since 2001. If you’ve been asking, “What does a heat pump do?” or “How can it help me?”, or need any other kind of assistance, schedule service online or call 602-737-3279 today.

About the Author

Chris Hays

Founder of Hays Cooling, Heating & Plumbing

Chris and Stacia Hays, are the founders of Hays Cooling, Heating & Plumbing; a family operated HVAC company in Phoenix founded in 2001 that services both commercial and residential customers. Chris leads a team of certified technicians who have over 45 years of combined experience and has earned and A+ rating with the BBB and a strong five star rating online. Hays Cooling, Heating & Plumbing focuses on providing support to their customers every step of the way, with exceptional service and competitive prices. If you are looking for top-notch air conditioning and heating service, contact Hays today.