Cooling: a unique advantage of heat pumps over boilers
When most people think about heat pumps, they think about heating their homes efficiently during winter. However, one of the biggest advantages of modern heat pump technology is that it can also provide cooling during warmer weather. If you're wondering, "Can I cool with a heat pump as well as use it for heating and hot water?" then the answer is a resounding yes!
Both air source and ground source heat pumps can provide effective cooling, helping homeowners maintain comfortable indoor temperatures throughout the year while benefiting from a single, energy-efficient system.
Active and passive cooling - two different ways to cool with a heat pump
Active cooling is where the heat pump compressor is used to actively cool the water in your heating system. Both air and ground source heat pumps can be used for this kind of cooling. Air source heat pumps do this by reversing the refrigerant circuit so that heat is taken from the water in the heating circuit inside the house and pushed outside by the fan unit, cooling the underfoor or fan coil emitters, which then cool the house. With ground source heat pumps the heat pump itself does not reverse but the system is set up to take the energy from the cold side via hydraulics when in cooling mode.
Passive Cooling
One unique advantage of some ground source systems is passive cooling.
Because the ground remains relatively cool throughout the summer, a heat exchanger can transfer excess heat from the property directly into the ground without the compressor operating.
The result is:
- Lower energy consumption than active cooling
- Reduced running costs
- Gentle, comfortable cooling
- Improved summer comfort
For homes with suitable ground loops or boreholes, passive cooling can be an exceptionally efficient solution.
The technical capabilities of air and ground source heat pumps for cooling
- The heat pump can cool only if the outside air temperature is above +15°C
- The heat pump can cool the water flowing to +7°C (for fan coil radiators) and +18°C (for underfloor systems).
It is important to understand that heat pumps designed primarily for heating, whilst very effective at providing summer climate control for your home, are not designed for jobs where you might want very cool temperatures or year round cooling (wine cellars for example).
The image below shows data from a real UK system operating during three hot August days. You can see that the temperature in the house is maintained at a comfortable level despite the fluctuating outside air temperature.
The black line shows the external air temperature.
The pale blue line shows the temperature inside the house.
The red line shows the temperature of the water flowing through the underfloor system on the ground floor.
The yellow line shows the temperature of the water flowing through the fan coil radiators on the first floor.
The four red and yellow ‘spikes’ show when the heat pump switches to heat up the hot water tank (most systems running with a single heat pump will only be able to do one function at a time and wll switch between them - a cascade of two or more heat pumps is required if continuous operation is essential). As can be seen in this well designed system, the demands for hot water are not so high or lengthy that the house temperature flunctuates dramatically.
Is heat pump cooling as effective as air conditioning?
The answer depends on the system design and your expectations.
Traditional air conditioning systems are designed specifically for rapid cooling and can achieve very low room temperatures quickly.
Heat pump cooling focuses on maintaining comfortable temperatures efficiently over longer periods
For many UK homes, a properly designed heat pump cooling system provides more than enough cooling to maintain comfort during summer. In some cases, fan coil units connected to a heat pump can deliver performance very similar to conventional air conditioning.
Heat pump cooling vs air conditioning. Which is better?
What are the pros and cons of cooling with an air or ground source heat pump compared to an air-to-air heat pump air conditioning system?
Many homeowners researching heat pump cooling ask how it compares to a traditional air-to-air heat pump air conditioning system. While both technologies can cool your home, they work differently and offer different benefits.
The right choice depends on whether your priority is whole-home heating and cooling, installation cost, energy efficiency, or achieving very low indoor temperatures during hot weather.
Pros of cooling with an air source or ground source heat pump
Using an air or ground source heat pump means you can have one system for heating and cooling.
One of the biggest advantages of using an air source or ground source heat pump for cooling is that the same system can provide both heating and cooling throughout the year.
Rather than installing a separate heating system and air conditioning unit, homeowners can benefit from a single low-carbon solution that delivers year-round comfort. For most UK homes space is at a premium and the advantages of a unit that can offer heating hot water and cooling in one are manifest. Most air to air systems, whilst they can also provide room heating, can don't offer hot water generation.
More discreet appearance
Many heat pump cooling systems use underfloor cooling, concealed fan coils, or existing hydronic distribution systems, meaning there may be fewer visible indoor units than with a traditional air conditioning system.
This can be particularly appealing in modern homes where aesthetics are important or those with historic features to preserve.
Potentially lower running costs
Ground source heat pumps can offer particularly efficient cooling, especially where passive cooling is possible. By transferring heat directly into the ground, cooling can often be delivered with very little electricity consumption.
This can make ground source cooling significantly more economical than conventional air conditioning in some applications.
Improved comfort
Cooling delivered through underfloor systems or low-temperature emitters tends to be gentle and evenly distributed.
Unlike air conditioning systems that can produce noticeable cold air movement, heat pump cooling often provides a more subtle and consistent indoor environment.
If you're looking for a complete heating, hot water and cooling solution, an air source heat pump or ground source heat pump with cooling capability may be the best long-term choice.
If your main objective is achieving powerful cooling during hot weather, an air-to-air heat pump air conditioning system may deliver faster temperature reductions and greater cooling flexibility. Upfront costs of this type of system can also be lower.
What kind of heat pump do I need for cooling?
For effective heat pump cooling, you will typically need:
A reversible heat pump
The heat pump must be designed to operate in both heating and cooling modes. All our current range comes with this capability as standard, but it's important to confirm during system selection as a heat pump needs suitable system components to work with to perform cooling.
Suitable heat emitters
Traditional radiators are designed primarily for heating and are generally not suitable for cooling.
The best cooling performance with our heat pumps is usually achieved with fan coil units and/or underfloor cooling systems (for active cooling with ground source systems you must use some fan coils). Fan coil units have condensate drains which allow then to operate below the dewpoint without the build up of condensation, making them particularly effective where lower temperatures are required - for example for lower night time temperatures in bedrooms.
Other options for cooling such ceiling heating systems and concrete core activation can be considered for new build properties.
A suitable cyclinder
Not all DHW tanks - not even all those designed for use with heat pumps - are suitable for operating in cooling mode. This is an important component to ensure is specified correctly if you want to use your system for cooling as it can expensive and difficult to change at a later date.
Condensation management
When cooling surfaces become colder than the surrounding air, condensation can form.
A properly designed cooling system will include controls and sensors to prevent condensation from occurring on floors, pipework or emitters. One of the advantages of STIEBEL ELTRON heat pumps is that the humidity sensors are included as standard with our heat pump controllers.
Professional system design
To achieve comfortable cooling without compromising efficiency, the system should be carefully designed around the property's cooling demand, insulation levels and occupancy patterns. Cooling demand calculations should be prepared by your installer alongside the heat loss calculations they prepare to ensure the heat demand of your property will be met by the system design.