How do heat pumps work?
Heat pumps are a cleaner, cheaper, and more energy-efficient alternative to traditional heating systems like gas or oil boilers. Unlike fossil fuel-based systems, they don’t burn fuel. Instead, they transfer heat energy from the air, ground, or water to provide central heating and hot water.
This process makes them 4X more energy efficient than a gas boiler and slashes energy costs by up to £550 a year. In this guide, we'll break down its key components, types, and benefits for homeowners looking to reduce their carbon footprint and energy bills.
What is a heat pump?
A heat pump is a highly energy-efficient system that moves thermal energy from one place to another to heat homes and provide hot water. Using renewable energy sources such as the air, ground, or a body of water, heat pumps significantly cut carbon emissions compared to traditional heating systems.
And don’t worry about the cold. Modern heat pumps, like the Aira Heat Pump, are designed to work efficiently even in freezing temperatures, keeping your home warm while lowering your energy bills.
How do heat pumps work?
Think of a heat pump like a fridge. But in reverse. Instead of keeping things cool, it moves heat energy from a cooler environment to a warmer one.
Unlike a gas boiler or other traditional heating systems that generate heat by burning fuel, heat pumps use a refrigerant cycle to move heat, using a highly efficient, eco-friendly refrigerant (like the R290 refrigerant in Aira Heat Pumps).
This makes them much more energy-efficient and better for the environment.
A step-by-step guide to how a heat pump works
Step 1: heat absorption
The outdoor unit of an air source heat pump draws in air. The heat exchanger extracts heat from the air, which is then absorbed by a liquid refrigerant.
Step 2: compression & heat transfer
The refrigerant evaporates into a gas and enters the compressor, which increases its temperature and pressure. The hot refrigerant passes through a condenser coil and a second heat exchanger, where the heat is transferred to the home’s central heating system and hot water supply.
Step 3: cooling & recycling
The expansion valve lowers the refrigerant pressure, cooling it down before it re-enters the evaporator to repeat the cycle.
Types of heat pumps
There are three common types of heat pumps. Each type extracts heat energy differently, but all operate using the same fundamental process.
- Air source heat pumps (ASHP): Absorb heat from the air. These are the most popular.
- Ground source heat pumps (GSHP): Extract heat from underground.
- Water source heat pumps (WSHP): Use heat from rivers, lakes, or ponds.
Air source heat pumps: the most popular choice
The most common type of heat pump, an air source heat pump, absorbs heat from the air via an outdoor unit and transfers it indoors. They come in two forms:
- Air to water systems: Supply hot water and heat your radiators or underfloor heating. The Aira Heat Pump is an air to water heat pump.
- Air to air heat pumps: Directly heat indoor air without a hot water supply. Like an air conditioner in reverse.
Air source heat pumps are easier to install than ground or water source systems and provide excellent energy efficiency, even in cold climates.
See how an air to water heat pump works
Ground source heat pumps
Ground source heat pumps use underground pipes to extract heat from the earth. Since underground temperatures remain stable, they provide maximum efficiency, regardless of outdoor temperature. But installation is more expensive and complex.
Water source heat pumps
These systems extract heat from a body of water, such as a lake or river, making them highly energy efficient. However, they require specific site conditions and outdoor space, making them less common.
The key components of a heat pump system
Heat pumps are more advanced than traditional heating systems, especially with AI advancements like Aira Intelligence. But at their core, they’re built from components that have been around for decades. Here’s what makes them work:
Evaporator coil
An evaporator coil is a network of tubes filled with cool refrigerant. It passes the cool refrigerant across the first heat exchanger, allowing it to evaporate from a liquid into a gas.
First heat exchanger
The first heat exchanger is where heat from the external environment (air, ground or water) is efficiently transferred to the refrigerant inside the system.
Compressor
The compressor's job is to compress the refrigerant gas, boosting its pressure and temperature. The efficiency of this process is crucial for the heat pump's overall efficiency, as it determines how much heat the system can generate from each unit of electricity.
Condenser coil & second heat exchanger
The compressed refrigerant gas enters the condenser coil before passing across a second heat exchanger to heat the home's heating system.
Expansion valve
The expansion valve reduces the refrigerant's pressure, cooling it down further, and passes it into the evaporator coil for the process to begin again.
Do heat pumps work in winter?
One of the biggest myths about heat pumps? That they don’t work in cold weather.
The truth is, modern heat pumps are engineered to perform in temperatures as low as -25°C. Just ask Scandivia, where heat pumps are the norm. As are sub-zero winters.
Even in the coldest months, heat pumps outperform gas boilers in energy efficiency. And, with our industry-leading 15-Year Aira Guarantee, we promise our Aira Heat Pump will perform at least 4X more efficiently than a gas boiler.
With any heat pump system, proper installation, insulation, and larger radiators are important as they help minimise heat loss and maximise heat output.
Benefits of heat pumps
Now that you know how a heat pump works, it’s easy to see why they’re the future of home heating. They have so many benefits that make them so much better than traditional heating systems, including:
- Lower energy bills: Reduce energy bills by up to £550 a year compared to a gas boiler.
- Lower your carbon footprint: Because they use renewable energy sources, heat pumps can reduce your home’s heating CO₂ emissions by 100% when combined with a Clean Energy tariff.
- High Coefficient of Performance (COP): Heat pumps deliver around four units of heat for every unit of electricity used. A gas boiler? Less than one.
- Efficient in cold climates: Heat pumps have been proven to mantain comfort, even in freezing temperatures.
- Future-proof your home. Heat pumps can even add up to £8,000 to the value of your home.
Heat pump costs and installation
While the installation cost of a heat pump may be higher upfront, government grants like the Boiler Upgrade Scheme, which gives eligible homes £7,500 to switch, and high energy savings make them a smart investment.
Heat pump installers will assess the size of heat pump needed for your home, ensuring optimal performance.
Is a heat pump right for you?
For heat pump owners or those considering homes with heat pumps, the savings, energy consumption reduction, and environmental benefits make them an excellent choice.
When compared to heat pumps cost over time, they outperform traditional heating systems in both efficiency and sustainability.
Why upgrade to an Aira Heat Pump?
With design and installation of your system included, switching to an Aira Heat Pump can cost about the same as replacing a gas boiler.
But here’s the real difference: there’s 0% VAT to pay, a £7,500 government grant available, flexible finance options and energy savings from day one. All backed by our 15-Year Guarantee.
Get your heat pump quote
What type of house do you live in?
Learn more about heat pumps
How much is a heat pump?
Air source heat pumps have the power to slash your annual energy bills by up to £550. And they cost less than you think.
What are air to water heat pumps?
Air to water heat pumps use thermal energy to heat your home and water. But how do they work and how are they installed?
*£550 annual energy savings and 100% home heating CO₂ reduction are based on replacing a boiler with an Aira Heat Pump and switching to our Aira Zero tariff.
**Heat pumps increase value of your home by £8,000 source: Scottish Power and WWF, “Better homes, cooler planet: how low-carbon technologies can reduce bills and increase house value”, August 2022. Full report is available here.
