What is a Heat Pump? | How does a Heat Pump work?

The heat pumps are most common all over the world. A heat pump is an equipment that transforms mechanical energy into heat energy. The heat pump works on the thermodynamic principle (i.e., a cold fluid converts into warm fluid when it compresses in a small volume). If this pump works reverse (i.e., as the fluid expands, it becomes cold), the pump is known as a reverse heat pump. This represents that heat pumps and reverse heat pumps work on the same principle (i.e., heat transfer). In this article, we mainly discuss different aspects of the heat pump.

What is a Heat Pump?

The heat pump is an electrically operated pump that transfers heat from one area to another area. The heat pumps are typically used to remove heat from the ground or the air to heat a residential or workplace. However, a reverse heat pump uses to cool a specific room or building.

The heat pumps use compressors and a refrigerant to transfer heat from one area to another. The heat pump is a part of the HVAC system.

If you know the working of the air conditioning system, you can easily understand the working of the heat pump. The heat pumps work in a similar way as the air conditioning systems.

heat pump

When you install heat pumps for your office or hose, you don’t have to install a separate to cool or heat your house or office. Due to this reason, heat pumps are preferable over air conditioning (HVAC) systems and traditional heating ventilating.

These pumps don’t combust fuel to generate heat because they only transmit heat. Therefore, they have very high efficiency. Due to this reason, the heat pumps are more environmentally friendly compared to gas furnaces.

Exhaust air heat pumps, water source heat pumps, ground-source heat pumps, and air source heat pumps are the most common types of heat pump. These pumps may also use in the district heating system.

The efficiency of the heat pumps represents in terms of SCOP (seasonal coefficient of performance) or COP (coefficient of performance). If the numeric number is higher, the pump has higher efficiency, and it uses less energy or electricity.

The government of the United Kingdom announced that gas boilers must be completely replaced with heat pumps up to 2050, and selling of the gas boilers will be illegal after 2025. Due to this reason, heat pumps are getting popularity in the UK.

How a Heat Pump works?

A heat pump is an electrical equipment that delivers heat from a source (low-temperature area) to a sink (high-temperature area). A heat pump works on the heat transfer principle. A heat pump works in the following way:

Heat Pump working

  1. First of all, liquid refrigerant is transferred into the indoor coil via an expansion device. This indoor coil works as an evaporator.
  2. As the home or other building’s inner air blows through the coil, the refrigerant extracts heat from the air and reduces the air temperature. This cooled air blows through the ducts of the room and cools the room. As the refrigerant absorbs air thermal heat, the temperature of the refrigerant increases, and it transforms into the gas refrigerant.
  3. When the liquid refrigerant converts into the gas refrigerant, it transfers into the compressor. The compressor compresses the gas refrigerant; due to that, the temperature and the pressure of the gas become very high.
  4. After the compression process, the compressed gas refrigerant transfers into the outdoor coil.
  5. These outdoor coils work as condenser coils that reduce the compressed gas temperature and again convert it into liquid refrigerant. There is an outdoor fan to transfer outside air (i.e., atmosphere air) into the outdoor coils. The atmospheric or surrounding air of the home has low temperature than the compressed gas temperature. Therefore, the heat of the compressed gas refrigerant transfers into the surrounding air via outdoor coils. After heat transfer, the gas refrigerant transforms into liquid. This liquid refrigerant is transferred from the outdoor coil to the expansion valve for further process.
  6. As the hot liquid refrigerant enters the expansion valve, it expands the refrigerant and reduces its pressure. This process quickly converts the hot liquid refrigerant into cold liquid refrigerant. As the refrigerant cools, it pumps back into the indoor coil, and the whole cycle repeats.

Working of Reverse Heat Pump

The reverse heat pump works on the heating cycle. This pump is installed in the room or building, which needs to be warmed. In the heating cycle, the pump takes heat from the environment and moves it into a room. The heating cycle works in the following way:

Reverse Heat Pump working, heating cycle

  • First of all, the liquid refrigerant introduces into the outdoor coils, where it extracts heat from the outdoor air. Due to the heat transfer process, the temperature of the refrigerant increases, and it converts into the gas refrigerant.
  • The gas refrigerant introduces into the compressor, where it compresses. Due to the compression process, the gas refrigerant pressure and temperature become very high. 
  • The hot gas transfers into the indoor coils that act as condenser coils. These coils take heat from the hot gases and transfer this heat inside the room. Due to this heat transfer process, the inner temperature of the room becomes high, and it warms up. 
  • After this process, the refrigerant enters the expansion valve, where it cools and converts into liquid form. After this process, the liquid refrigerant is sent back into the outdoor coils, and the whole cycle repeats.

For better understanding, watch the following video:

Parts of Heat Pump

The heat pump has the following most major components:

  1. Expansion valve
  2. Compressor
  3. Indoor unit
  4. Refrigerant
  5. Outdoor unit

An expansion valve uses to regulate the flow of the refrigerant.  As the name of the expansion valve represents that it uses to expand the refrigerant.

When the refrigerant expands inside the expansion valve, its pressure and temperature become low, and it cools.

Read More: Different types of Valves


The purpose of the indoor unit is the same as the outdoor unit, i.e., heat transfer from outside to inside the room or vice versa. It has a fan and a coil.

The coil works as a condenser (in a heating cycle) or evaporator (in a cooling cycle). The fan uses to blow air across the coils and throughout the ducts of the house.  


The outdoor system has a fan and a coil. This coil works as either an evaporator (in a heating cycle) or a condenser (in the cooling cycle). The fan uses to blow surrounding air on the coils to transfer heat.


A refrigerant is a substance that plays a most vital role in cooling or warming the room. It circulates throughout the pump system. It absorbs heat and transfers this heat inside the room through the heat transfer process.  


The reverse valve uses in the reverse heat pump. It allows the refrigerant to flow in a reverse direction.


The main objective of the compressor is to compress the refrigerant and increase its pressure and temperature. The heat pumps use different types of compressors, and some of them are given below:

Read More: Different types of Compressors

Types of Heat Pumps

The heat pump has the following major types:

  1. Air source pump
  2. Solar-assisted pump
  3. Geothermal heat pump
  4. Water source pump
  5. Exhaust air pump
  6. Hybrid pump
  7. Ductless pump

1) Air Source Heat Pump

The air source heat pump gets heat from a low-temperature area and transfers it to your room or home to increase its temperature. 

This pump uses to transfer heat between two heat exchangers. The first heat exchanger is installed outside the room, which has multiple fins and a fan used to blow air through the fins, and the other heat exchanger uses to warm up the inner air of the room directly or heats water which then uses heat emitters to circulate the heat across the room and transfers heat in the room.

air source heat pump

This air pump also uses to cool the room or building. This type of pump can also work as a reverse heat pump which works on the cooling cycle. In the case of this pump, the internal heat exchanger uses to remove the internal heat of the room and cools the room.

These types of heat pumps have the same design as the air-conditioning systems. The size of these pumps varies according to the heat requirements.

These pumps have low costs, and easy installation, and easy operation. Therefore, they are most widely used all over the world. The cost of the air source heat pump system is from $10,500 to $18,975.

Advantages of Air Source Heat Pumps: –

  1. These types of pumps have an easy Installation
  2. They have a long service life.
  3. They require low maintenance.
  4. There is no need of fuel storage because this pump uses surrounding air as fuel.

Disadvantages of Air Source Heat Pumps: –

  1. These pumps deliver low heat than oil and gas boilers.
  2. They need larger radiators.
  3. It has high operational noise as an air conditioner.
  4. They need to be run continuously in the winter, which increases the electricity bill cost.
  5. The air source heat pumps have low COP.
  6. It has lower efficiency during winter.
  7. If you live on a gas main, the air source heat pumps are not the best suitable.

2) Geothermal Heat Pump

A ground-source heat pump or geothermal heat pump system gathers heat by the groundwater or soil and transfer this heat to the room which is to be heated. It maintains a comparatively constant temperature lower than 9.1 m (30 feet) depth throughout the year.

Geothermal heat pumps

These pumps usually have a coefficient of performance (COP) of 4.0 at the heating season’s start and a seasonal COP up to 3.0 when heat is extracted by the ground. These pumps have very high installation costs.

These types of pumps can also use for cooling a room or building. For cooling a building, it absorbs the heat of the room or building and transfers it to the ground via a ground loop.

Advantages of Geothermal Heat Pump System 

  1. There are environmentally friendly.
  2. It uses geothermal energy, which is a renewable energy resource.
  3. There is no need of fuel storage.
  4. Geothermal is a source of energy that will not be ended until the destruction of the earth.
  5. The energy produced by this geothermal may be easily calculated because it fluctuates differently than other energy sources (i.e., wind and solar). This allows the production of geothermal power plants to be predicted very precisely.
  6. Geothermal supplies consistent energy than other renewable resources such as solar energy and wind energy. In contrast to wind and solar energies, the earth always has resources for developing and using geothermal energy.

Disadvantages of Geothermal Heat Pump System

  1. The geothermal heat pumps are installed in a fixed place where geothermal energy is available.
  2. Geothermal energy has a high cost.
  3. These pumps have high installation costs.

3) Exhaust Air Pump

This pump obtains heat from the room’s exhaust air and supplies it inside the room or building. This type of heat pump needs mechanical ventilation. It needs a specific rate of air exchange in order to maintain its performance.

Exhaust air heat pump

The exhaust air heat pumps have the following types:

  1. Exhaust air-water heat pump that transfers heat to heating circuits, including hot water storage tanks.
  2. Exhaust air heat pumps that deliver heat to the intake air.

Advantages of Exhaust Air Heat Pumps

  • This pump reduces the electricity bill.
  • You can earn money by RHI (Renewable Heat Incentive).
  • It generates low noise.
  • It has a compact design.

4) Solar-assisted Heat Pumps

A solar-assisted heat pump (SAHP) is also known as a solar heat pump. This pump uses solar energy to heat the building or heat the water. A SAHP system is a device in which solar thermal panels and a heat pump are integrated into a single system.

In this system, the solar panel acts as a cold heat source and uses to transfer the generated heat to the heat pump’s evaporator.

Solar Heat Pump

These pumps have low cost, produce highly efficient energy, and have high COP.  

The solar heat pump system has the following two main operating modes:

  1. Direct heating: In the direct heating method, solar energy is directly used to warm up the room or building if the stored heat has a sufficiently high temperature.
  2. Indirect heating through heat pumps: An indirect heating method is utilized when the stored heat doesn’t have the adequate temperature for direct heating. In this method, a heat pump uses to fulfill the heating requirements. The pump gets solar energy and transforms it into useful heat.  

5) Water Source Heat Pumps

This pump operates in the same way as a geothermal heat pump, except that the water source pump uses water energy instead of ground energy. This pump extracts heat from the water and transfers this energy to the desired room or place.

Water source heat pump

The working principle of these heat pumps is very similar to the air source heat pumps.  

The water source heat pumps perform the heat transfer process by passing the water via a series of tubes. When water circulates, it collects heat from lakes and reservoirs and transfers it to your room or building.  

During the summer season, these pumps process in the reverse direction (i.e., the heat is extracted from the room or building and released into the external cold water). The cooling heat pumps have high efficiency than the heating cycle heat pumps.

Advantages of Water source Heat Pumps

  1. This is an energy-saving pump.
  2. This pump doesn’t require large ventilation pipes, no insulation, a freezer room, and circulating water pipes.
  3. It has a relatively low cost.
  4. These pumps have low maintenance costs.
  5. These have easy installation.

Disadvantage of Water Source Heat Pump System

  1. During the transition period, you cannot make optimal use of the fresh air.
  2. These types of heat pumps generate high noise.
  3. The device is mainly installed on the ceiling, which makes maintenance difficult.

6) Hybrid Heat Pumps

A hybrid heat pump utilizes a combination of fossil fuels and renewable energy to warm the room or building.

These heat pumps absorb heat from various sources according to the external temperature.

Hybrid heat pump

These pumps use air heat when the room’s external air temperature is more than 4-8 degrees Celsius and use groundwater as a heat source when the temperature is low. In case when heat pump doesn’t work, the hydraulic systems can also store summer heat by moving groundwater into an air exchanger.

7) Ductless Heat Pump 

A ductless heat pump is also known as a mini-split pump. These pumps have an easy operation and are less expensive.  It has cost from $1,200 to $9,000. A concrete pad is also required to install this pump which has cost up to $130.

Ductless Heat Pump

Maximum large buildings prefer ductless mini-splits that want convenience and flexibility in their cooling and heating system.

How to Increase the Efficiency of Heat Pump?

  1. Don’t rely on emergency heat: You don’t turn on emergency heat mode in normal conditions. Turn on this mode only for real emergencies. This mode reduces the efficiency of the heat pump and increases the utility bill.
  2. Keep your filter clean: Air filters play a big role in the performance of the heat pumps. As the heat pump sucks air from the environment, the air filter firstly removes the debris and other solid particles from the air and then transfers this clean air to the compressor of the heat pump. If you do not properly clean the filters, the contamination particles will be trapped into the filters, and the pump will need to work hard. In this way, the pump efficiency and service life are reduced.
  3. Clear leaves and debris from your outdoor unit: The outdoor unit must also be able to let the air circulate freely. For best performance, regularly remove dead leaves, debris, and other contaminations from the outdoor units of the system.
  4. Do not cover your system: The heat pumps are designed for outdoor use, and you shouldn’t cover them in winter. If you cover your system in winter, it may produce some severe issues such as insect and mold growth infestation. Only leave the ice in the cold season. This is a serious hazard to you, and your unit and your system must be operated in defrost mode.
  5. Don’t worry about the defrost mode: You don’t need to worry about the defrost mode. This mode is a part of the heat pump cycle in normal winter operation. However, this cycle completes in just a few minutes. If your system has been in defrosting mode for a long time, you need to repair it immediately.
  6. Maintenance of the Heat Pump: For an efficient operation of your system, you must perform the maintenance and cleaning of your system at least once a year.

How Much Does Heat Pump Cost?

The new heat pumps have high installation costs. This cost varies according to the region or area where you live and the type of pump which you want to buy.

The average installation cost of a heat pump is from $10990 and $61850. The installation cost of the air to water heat pump is from $9600 to$15120.

The installation cost of an air source heat pump varies between $10300 and $26120. The geothermal heat pump installation cost varies between $27480 to $48110.

The below-given table represents the average cost of different heat pump types:

TypeUnit CostInstallation Cost
Gas-Fired Pump$2,090 to $6,010$1,200 to $2,100
Ductless Mini-Split$1,100 to $3,600$400 to $1,600
Geothermal Heat Pump$2,080 to $6,100$91,000 to $30,000
Air-Source$2,010 to $5,600$1,200 to $2,100

As you can see, geothermal or ground source heat pumps have a high cost compared to other types of heat pumps.

What is the Heat Pump repair cost?

The repair cost of the heat pump is given below according to the repair type:

Repair TypesAverage Cost
Compressor and condenser$1,400 to $4,600
Ductwork$740 to $3,400
Thermostat$90 to $260
Defroster repairs$90 to $660
Leaks$80 to $620
Clear blockage$70 to $160
Electrical work$90 to $610

Advantages and Disadvantages of Heat Pumps

The heat pump has the following advantages and disadvantages:

Advantages of Heat Pump

  • These are electrically operated pumps.
  • The heat pumps have low operating costs.
  • They require lower maintenance.
  • This pump has a long service life.
  • It provides excellent safety.
  • It decreases the emission rate of Carbon.
  • The heat pumps have a dual function (i.e., both cool and warm the room according to the requirements).

Disadvantages of Heat Pump

  • These pumps have complicated installation.
  • They have high upfront costs.
  • They generate problems in cold weather.
  • These pumps don’t have excellent sustainability.

Applications of Heat Pump

  1. The heat pumps are used in the HVAC systems.
  2. They use to heat the buildings.
  3. The reverse heat pumps are to cool the different areas of the residentail and commerial buildings.

Heat Pump Vs AC

The main difference between a heat pump and an air conditioner system is given below:

Heat PumpAir Conditioner
A heat pump can cool or warm up the building.An air conditioner can just cool the building. It can’t heat the building.
The indoor heat pumps have a lower cost than AC.The air conditioners have high costs.
These pumps use lower electricity than air conditioners in cooling mode.They use higher electricity in cooling mode.
It has high efficiency.It has low efficiency.

Who makes the best heat pump system?

Following are the most famous brands that manufacture the best heat pumps:

BrandOutput CapacityComponentsPrice/ValueEfficiency
Trane60,000 BTUsVery GoodVery AffordableUp to 20 SEER
RUUD60,500 BTUsExcellentExcellentUp to 23.5 SEER
Goodman59,500 BTUVery GoodExcellentUp to 19 SEER
Rheem60,500 BTUsVery GoodVery GoodUp to 20 SEER
York2 to 5 tons Very GoodVery GoodUp to 20 SEER
Lennox60,500 BTUExcellentGoodUp to 23.5 SEER
Coleman 60,000 BTUExcellentGoodUp to 20 SEER
Amana 52,000 BTUVery GoodVery GoodUp to 21 SEER

FAQ Section

What is COP?

The COP stands for coefficient of performance. The COP of an air conditioning system or heat pump is a ratio between the heat supplied or removed by the desired system (Q) and the work needed by the desired system (W). The coefficient of performance uses to represent or measure the efficiency of the heat pumps or air conditioners. If the COP value is higher, the air conditioning system will be higher.

Can the COP of a heat pump vary?

The COP of the heat pumps varies according to the ground temperature (inlet temperature) and the temperature needed to heat up the radiator or underfloor (outlet temperature).

At what temperature does a heat pump lose efficiency?

A heat pump doesn’t work efficiently when temperatures are from 25 to 40 degrees Fahrenheit. As the outdoor temperature becomes more than 40 degrees Fahrenheit, the heat pumps work efficiently. When the outdoor temperature drops less than 40 degrees Fahrenheit, the pump efficiency starts decreasing.

Which brand of heat pump is the most reliable?

The following are some brands that are most reliable:

  1. Trane
  2. Amana 
  3. Coleman
  4. RUUD
  5. Lennox
  6. Goodman
  7. York
  8. Rheem

What does a heat pump look like?

In most cases, a heat pump has two parts. The first part contains an indoor unit that involves a fan, a supplemental heater, and indoor coils. The second part contains an outdoor unit with a fan, reversing valve, compressor, and outdoor.

The looking of the indoor unit is very same as the gas furnace. An outdoor unit of the heat pump looks very similar to a central air conditioner.

How much does it cost to install a heat pump?

The installation cost of the heat pumps varies according to the area where you live and the brand which you want to purchase. The average heat pump installation cost is from $4000 to $7200. The geothermal pump has $11,000 to $31,000 installation cost. The ductless heat pump system cost varies from $1900 to $14,600.

Which type of heat pump is most efficient?

Only geothermal heat pumps are the most efficient pumps. These pumps are environmentally friendly and efficient. However, they have very high costs because they have time-consuming and complex installation. They consume less energy than other traditional heat pumps.

How many mini split heat pump systems would a house with four main atoms typically use?

One minisplit system in each room. It means you need to use four mini-split systems for four rooms.

When running my heat pump which mode the pump needs to be on?

In case of an emergency, you must turn ON the emergency heating mode of your heat pump when your pump doesn’t work in winter. If this mode is not turned ON, your pump will consume electricity; due to that, your electricity bill will be higher. 

Read More
  1. Different types of Pumps
  2. Different types of Compressors
  3. Working and types of Solar Pumps
  4. Types of Boilers

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