How Does a Heat Pump Work? – Informational Guide

| Last Updated: September 13, 2023

A heat pump comes in handy at home, business premises, or office due to its versatility in heating, cooling, and even dehumidification. Although the underlying concept is the same, a heat pump achieves its functions in slightly different ways, depending on what you want to do.

Learning how a heat pump works may seem challenging at first because of the different system manipulations. Now that you are here, let's learn the inner bits of the workings of a heat pump in cooling and heating your indoor spaces like homes and offices.

Be sure to read through to the end for a comprehensive understanding to ensure you use your heat pump efficiently all the time.

What is a Heat Pump and What is it Used For?

A heat pump is an electrical heating, ventilation, and air conditioning (HVAC) appliance that transfers heat from a location to another. It uses very little electrical energy to move the heat. 

Unlike other heating solutions like boilers, heat pumps are more environmentally friendly. 

Heat pumps do not create heat. They only move existing heat from one place to another based on the natural tendency of heat transfer in which heat flows from a high-temperature location to a low-temperature location.

Heat pumps are used for several functions, including heating, cooling, and dehumidification of indoor places. Some are even used for heating domestic water for everyday use, especially for bathing.

The popularity of heat pumps owes to the versatility in their usage, with heating and cooling being the most common uses. They are unlike air conditioners that only help improve air quality. Heat pumps can even heat rooms using heat from outside air, even in winter. 

Heat Pump Components

There are several types of heat pumps, and the components may vary slightly from one kind to the other. However, air-source heat pumps are the most common. A heat pump comprises the following major parts.

  • Thermostat: It allows you to set your preferred temperature for the pump's operation.

  • Refrigerant: It is the fluid that circulates between the indoor and outdoor unit through the refrigeration lines.

  • Pipes and refrigeration lines: These connect the outdoor unit and the air handler inside the house.

  • Ducts: These are the air tunnels in various places inside the home. Not all heat pumps involve using the ducts in your home or installing new ones where none exist. 

  • Thermostatic expansion valves: They regulate the flow of refrigerant for effective reduction of the coolant temperature and water.

  • Condensing unit: It is responsible for pressurizing the coolant or refrigerant and moving it within the system.

  • Reversing Valve: As the name suggests, this valve reverses the flow of the refrigerant to change the function of the system between cooling and heating.

  • Control panel or board: It allows you to program the heat pump between defrost, cooling, or heating modes. 

A typical air-source heat pump comprises an indoor unit and an outdoor unit. The indoor unit is also known as the air handler and fan and a coil that acts as an evaporator in the cooling mode and a condenser in the heating mode.

The outdoor unit also has a fan and a coil that acts as an evaporator in the heating mode or a condenser in the cooling mode.

Just like a ground source heat pump, a water source heat pump is also more complicated and will have more components other than the typical ones mentioned earlier. 

Such extra parts may be the desuperheater, water, or an antifreeze mixture in the ground loop (network of pipes).

How Does a Heat Pump Work?

To best understand how a heat pump works, it is best to break down its functionality to reflect the exact activity it does at a given time. 

How Does a Heat Pump Work In the Winter?

In the winter, you will need your heat pump for heating your indoor space. A heat pump heats your area when the indoor coil works as the condenser and the outdoor coil works as the evaporator. 

As the refrigerant flows between the two units, the condenser coil absorbs heat from the outdoor air and releases it to the indoor evaporator coil. The refrigerant absorbs heat energy from the air drawn in by the condenser coil. 

The now warm air travels throughout the home through the ducts or air vents, increasing the temperature in your home. The refrigeration cycle runs again until it achieves the desired thermostat temperature setting.

How Does a Heat Pump Work In the Summer?

A heat pump cools indoor living spaces in the summer. The fan in the indoor unit draws in the warm interior air. The refrigerant absorbs the heat from the warm air as it passes between the outdoor condenser coil and the indoor evaporator coil. 

The now cooled air is blown through the ducts or air vents throughout your home to lower the temperature. 

Unlike during heating, when the outdoor air is the source of the heat energy, the cooling mode involves sucking the heat energy out of the air in your home and channeling it outside where the air is even hotter.

It's a reverse process that forces heat transfer from a low-heat to a high-heat location. 

How Does a Ground-Source Heat Pump Work?

A ground-source or geothermal heat pump also works based on the principle of heat transfer from the ground, which is either heated up by the sun or has its own heat even when it is cold. 

The ground-source system has a network of underground pipes carrying the refrigerant that transfers the heat from the ground to the indoors or vice versa, depending on what you want the heat pump to do. 

Closed-loop ground-source heat pumps have an antifreeze solution circulating in the system to prevent freezing in cold weather. 

During heating, the heat absorbed from the ground is distributed inside the house using radiators, underfloor heating systems, forced-air systems, or others. 

How Does a Water-Source Heat Pump Work?

A water-source heat pump can also heat or cool your indoor space. When heating, the pump transfers heat from a suitable water body, like a river, borehole, surface lake, or well. 

In a closed-loop water-source system, a mixture of antifreeze and water channels to a water mass. It flows the heat exchanger or coils in the water to allow for the heat exchange process. The now warm mixture channels to the heat pump, and the heat is exchanged. 

In an open-loop water-source system, water is extracted from the source and channeled directly to the heat pump. The refrigerant absorbs the heat energy in the water, then the water flows back to the water body. 


Understanding how a heat pump works helps you ensure that you use your heat pump efficiently and correctly for heating, cooling, or dehumidifying your residential, office, or business space. 

Although the components may differ across different heat pump types, the underlying working concept of heat transfer applies to each heat pump. 

People Also Ask

Heat pumps are quickly gaining popularity in most places because of their versatility. Whether you are a new user or a regular, here are two common questions to help you with the operational dynamics of heat pumps. 

Do Heat Pumps Use a Lot Of Electricity?

As long as your heat pump operates efficiently or normally without struggling, its electricity consumption remains very low. 

If you notice an undue increase in how much electricity the system uses, seek the help of a qualified HVAC technician to troubleshoot and repair the heat pump to restore its efficiency.

At What Temperature Does a Heat Pump Stop Being Effective?

Most heat pumps operate well at temperatures above 40°F. The output or efficiency of the device drops as the temperatures drop below this ideal level. 

In the cold season, your heat pump can still absorb heat energy from the outdoors, but this is limited when the temperatures drop below freezing. At about -13°F, a heat pump has about 76% efficiency. Some pumps even stop entirely when the temperatures go to as low as -18°C.

My name is Bob Wells and I am a retired HVAC tech from Washington state. I am currently retired and no longer do much with HVAC, however, I feel like I have a lot of knowledge in the subject and I wanted to create a website where I could talk about what I've learned and help upcoming HVAC techs. Find more info about me and HVAC Training 101.