When frost appears on the ground, and energy bills start creeping up, many homeowners ask the same question: Do heat pumps work in cold weather?
The short answer is yes.
Even during a cold snap in Kent, a modern air source heat pump will work effectively. These systems are designed to draw usable heat from the outside air, even when temperatures fall below freezing, and transfer it indoors to keep your home warm.
That said, performance depends on how well the system is designed for your property. The right heat pump size, radiator setup, insulation, flow temperature, and controls all affect how efficiently your home stays warm through winter.
How do heat pumps work when it’s cold outside?
An air source heat pump works a bit like a fridge in reverse. Instead of pulling heat from a chilled space, it captures heat from the outside air and brings it into your home.
That heat is then compressed to a higher temperature and circulated through your radiators, underfloor heating, and/or hot water cylinder to keep everything warm.
Even in freezing conditions, there's still heat in the air to tap into. A well-designed system can use this to maintain a steady, comfortable temperature indoors.
What happens to heat pump efficiency in winter?
Heat pumps can work in cold weather, but they usually use more electricity in winter than in milder months. This is expected. As outdoor temperatures drop, your home loses heat more quickly, so the heating system has to run for longer or work harder to maintain a steady indoor temperature.
A heat pump’s efficiency is often measured using COP, which stands for coefficient of performance. A COP of 3 is an average benchmark, meaning the system produces 3 units of heat for every 1 unit of electricity it uses.
But, in reality, COP isn't a fixed number. It changes depending on outdoor conditions and how much work the system has to do. So, in milder weather, when the temperature difference between outside and inside is smaller, a heat pump can operate more easily, and efficiency is often higher.
Conversely, as temperatures fall, the system has to work harder to extract heat and raise it to the required indoor temperature, so the COP will usually drop.
This is where system design makes a clear difference. An air source heat pump that's:
- Correctly sized for the property
- Paired with suitable radiators or underfloor heating
- Set up with the right controls
...can maintain steady, efficient performance across changing conditions. Without that design work, the system may need to work harder than necessary, which can affect both comfort and running costs.
Do heat pumps work below freezing?
Yes, modern heat pumps are designed to keep working even when temperatures drop below freezing.
During colder spells, you may notice the outdoor unit running a short defrost cycle. This is a normal part of operation and helps maintain performance by preventing ice build-up.
A common concern is that freezing temperatures will stop a heat pump altogether. In typical UK conditions, that shouldn’t happen when the system has been properly specified.
What matters most is how well the system has been designed for your home. A professional installer will calculate heat loss for colder days and size the system accordingly, so it can continue to provide reliable heating even as temperatures fall, which moves us on to our next section nicely...
Why heat loss calculations matter
A heat loss calculation shows how much heat your home loses through walls, windows, floors, roofs, doors, and ventilation. This forms the basis for designing a system that keeps your home warm, even in colder weather.
To do that accurately, a proper survey looks at:
- The size and layout of your property
- Wall, roof, and floor insulation
- Window and door performance
- Existing radiators or underfloor heating
- Hot water demand
- Preferred indoor temperatures
- Current heating use and costs
All of this information is used to determine the appropriate heat pump size and the heat output required for each room.
This step matters because getting the sizing wrong can affect performance. An undersized heat pump may struggle to meet demand during colder periods, while an oversized system can cycle too frequently and run less efficiently.
That’s why, at SGS Energy, we offer free heat loss reports to many customers before installation. It helps build a clear picture of your home’s needs and takes the guesswork out of system design.
Should you leave a heat pump on in cold weather?
Yes. Heat pumps work best when they maintain a consistent indoor temperature rather than being switched on and off throughout the day.
Turning the system off for long periods means it has to work harder to bring your home back up to temperature, especially during colder weather. Keeping it running allows it to maintain warmth more evenly and avoid those bigger energy spikes.
You can still adjust the temperature to suit your routine, but it’s generally more effective to reduce it slightly rather than switch the system off completely.
How to improve heat pump performance in cold weather
A well-designed heat pump should be ready for winter, but these steps can help improve performance:
1. Improve insulation where possible
Better insulation reduces heat loss, which means your heat pump has less work to do. Loft insulation, cavity wall insulation, draught-proofing, and better glazing can all help your home hold onto warmth for longer.
2. Check radiator suitability
Radiators need to provide enough heat at lower flow temperatures. Some may be fine as they are. Others may need to be replaced with larger models.
3. Keep the outdoor unit clear
Air source heat pumps need good airflow. So, keep leaves, snow, and debris away from the outdoor unit so air can move freely.
5. Book regular maintenance
A professional service will check refrigerant levels, controls, filters, electrical components, and overall system performance. Small issues are usually easier to fix before they affect comfort or running costs.
Will a heat pump save money in cold weather?
A heat pump can reduce energy use because it moves heat rather than creating it directly. Running costs, though, depend on several factors:
- Your current heating system
- Your electricity tariff
- Your home’s insulation
- The heat pump’s seasonal efficiency
- Radiator and pipework suitability
- How the system is controlled
- Your household’s heating and hot water demand
The UK Government’s Boiler Upgrade Scheme may also help reduce upfront installation costs. The scheme offers a grant of £7,500 towards eligible low-carbon heating systems, including air source heat pumps.
Common myths about heat pumps in cold weather
Myth 1: Heat pumps only work in new builds
Air source heat pumps work in many types of homes. That said, older properties may need insulation improvements or radiator upgrades, but age alone doesn't rule a home out.
Myth 2: Heat pumps make homes feel cold
A properly designed heat pump should keep your home just as warm as a traditional heating system.
What feels different is how that warmth is delivered. Instead of short bursts of high heat, a heat pump provides a steady, consistent level of warmth throughout the day. This avoids the cycle of rooms heating up quickly and then cooling down again.
In practice, that often means fewer cold spots and a more even temperature across the home. Once the system is set correctly, your home should feel consistently warm, even during colder weather.
If a property does feel cool, it’s usually a sign the system hasn’t been properly sized or set up for the space, rather than a limitation of heat pump technology itself.
Myth 3: Every radiator must be replaced
Some radiators may already be suitable. A heat loss survey will show where changes are needed.
Book a heat pump survey in Kent
So, do heat pumps work in cold weather? Yes (when the system is designed around your home).
If you’re considering an air source heat pump, the next step is understanding what your property actually needs. That’s where a heat loss report comes in.
At SGS Energy, we offer free heat loss reports for many customers (depending on property size and suitability). This gives you a clear picture of which system would work best and whether any changes are needed to support it.
Thinking about a heat pump for your Kent home? Get in touch to see if you qualify for a free heat loss report and take the first step towards a system designed for reliable winter comfort.
FAQs
Do heat pumps work in cold weather?
Yes. Air source heat pumps work in cold weather, including below freezing (-20°C).
Are heat pumps efficient in cold weather?
Heat pumps are usually less efficient in very cold weather than in mild weather, but they can still be highly efficient compared with many traditional heating systems. In fact, research shows that heat pumps can be more than twice as efficient as fossil fuel heating in cold temperatures.
Will I need new radiators for a heat pump?
Possibly. Some homes can use existing radiators, while others need larger radiators to work efficiently at lower flow temperatures. A heat pump survey will confirm what your home needs.
