Key takeaway
Yes, heat pumps work in winter, including when temperatures fall below freezing. An air source heat pump can still extract heat from cold outdoor air and use it to warm your home. However, colder weather affects efficiency, so the system needs to be designed for your property and its heating requirements.
If you’re considering a heat pump for your home in North Wales or Cheshire, it’s understandable to wonder how it will perform during a cold snap. Here’s what to expect, why system design matters and how to keep your heating working effectively through winter.
How Can a Heat Pump Extract Heat From Cold Air?
This is the question that puzzles most people. How can something cold possibly heat your home?
The answer lies in a simple principle: outdoor air contains heat energy even when it feels cold to us. At 0°C, there’s still plenty of thermal energy available. In fact, air only loses all heat energy at absolute zero (−273°C), which doesn’t occur naturally on Earth.
An air source heat pump works like a refrigerator in reverse. It uses a refrigerant, a fluid with a very low boiling point, to absorb heat from the outside air. A compressor then concentrates this heat and raises its temperature significantly.
In an air-to-water system, this heat transfers to water that circulates through your radiators or underfloor heating. The result is a warm home, powered primarily by the free heat energy in the air outside.
Do Heat Pumps Still Work Below Freezing?
Yes. Air source heat pumps are specifically designed to operate in sub-zero temperatures.
The systems we install at JM Renewables are built for British winters and colder climates:
Mitsubishi Ecodan
−20°C
Operating limit
Stiebel Eltron
−20°C
Operating limit
SIGENERGY
Year-round
Designed for cold conditions
These aren’t theoretical limits. These are the conditions the equipment is engineered and tested to handle.
However, there’s an important distinction between operating and operating at peak efficiency.
As outdoor temperatures drop, a heat pump works harder to extract the same amount of heat. This means efficiency decreases in very cold weather. But “less efficient” doesn’t mean “unable to heat your home.” A properly designed system accounts for cold weather performance and ensures your home stays warm even during the coldest days of the year.
The key factor isn’t whether the heat pump can technically run at −10°C. It’s whether the system has been correctly sized for your home’s heating needs in those conditions.
Will a Heat Pump Keep My House Warm in Winter?
This is really the question behind all the others. You don’t just want a heat pump that runs in winter – you want a home that stays comfortable.
The answer depends on how well the installation is designed for your specific property.
A heat pump isn’t a like-for-like boiler swap. It works differently, typically producing heat at lower temperatures over longer periods rather than short bursts of very hot water. This approach is actually more efficient, but it means the whole heating system needs to work together properly.
What We Check During a Home Survey
When we assess a property for a heat pump installation, we look at:
| Heat loss calculation | A room-by-room assessment of how much heat your home loses through walls, windows, roof and floors. This tells us the heating capacity you actually need. |
| Current heating system | What you’re replacing (gas, oil, LPG, electric) and how it’s distributed around the home. |
| Radiators and emitters | Whether your existing radiators can deliver enough heat at the lower flow temperatures a heat pump uses, or whether upgrades are needed. |
| Hot water requirements | How much hot water your household uses and the best way to meet that demand. |
| Outdoor unit location | Where the heat pump can be positioned for good airflow, minimal noise impact and proper drainage. |
| Insulation levels | The current state of your home’s insulation and whether improvements would significantly reduce your heating needs. |
| Controls and settings | How weather compensation and smart controls can optimise comfort and efficiency. |
This assessment ensures the system we recommend can actually keep your home warm on the coldest winter days, not just on paper, but in practice.
Do Heat Pumps Cost More to Run in Winter?
It’s reasonable to expect higher heating bills in winter, regardless of what system you use. Your home simply needs more heat when it’s cold outside.
With an air source heat pump, two things happen in colder weather:
- Your home loses heat faster, so more heating is needed
- The heat pump works harder to extract heat from colder air, reducing efficiency
This typically means higher electricity use during winter months compared to autumn or spring.
However, comparing winter bills alone doesn’t tell you whether a heat pump costs more than your previous heating system. You need to compare like with like, the same cold period, accounting for the fuel you’ve replaced.
| Homeowner question | What to understand |
|---|---|
| Will it keep heating below freezing? | A properly sized system continues operating in sub-zero conditions |
| Will efficiency stay the same? | Efficiency generally decreases as outdoor temperatures fall |
| Will electricity use increase? | It typically increases because your home needs more heat and the system works harder |
Your actual running costs depend on several factors: your home’s heat demand, the system’s seasonal efficiency, your electricity tariff, and how you use the heating controls.
Many homeowners find that switching from oil or LPG to a heat pump reduces their annual heating costs, even accounting for higher winter electricity use. Those on mains gas may see smaller savings or similar costs, depending on their circumstances.
Why Does My Heat Pump Frost Over in Winter?
If you look at your outdoor unit on a cold, damp morning and see frost or ice on the heat exchanger, don’t worry. This is completely normal.
Frost forms because the heat pump is doing its job. As the unit extracts heat from the air, the heat exchanger surfaces become colder than the surrounding air. When humidity is present, moisture condenses and freezes on these cold surfaces.
Your heat pump handles this automatically through a defrost cycle. The system temporarily reverses operation to warm the outdoor coil and melt the ice. You might notice:
- A change in the sound the unit makes
- Visible steam or vapour rising from the unit
- Water dripping from the base of the unit
All of this is normal. The defrost cycle typically lasts a few minutes before the system returns to heating mode.
What’s Normal vs What Needs Checking
Normal operation:
Temporary frost that clears during automatic defrost cycles
Brief periods of vapour or steam
Water discharge from the unit’s base
Worth contacting your installer about:
Temporary frost that clears during automatic defrost cycles
Repeated fault messages on the controller
Your home not reaching comfortable temperatures
Unusual noises that don’t resolve after defrosting
If something doesn’t seem right, contact JM Renewables rather than attempting to manually defrost the unit or change technical settings yourself.
Good drainage around the outdoor unit matters in winter. The water discharged during defrost cycles can freeze on the ground, so proper installation includes ensuring this water drains away safely.
How Can You Help Your Heat Pump Run Efficiently in Winter?
You don’t need to become a heating engineer, but a few simple practices help your system perform at its best:
Use the controls as recommended
Your installer will set up weather compensation and schedules suited to your home. Stick with these settings rather than constantly adjusting them.
Aim for steady warmth
Heat pumps work most efficiently maintaining a consistent temperature rather than letting the house go cold and demanding rapid reheating. This is different from how you might have used a gas boiler.
Keep the outdoor unit clear
Ensure nothing blocks airflow around the unit. Don’t stack items against it or allow plants to grow too close. If snow builds up around the base, gently clear it away.
Stay on top of maintenance
Annual servicing keeps everything running efficiently and catches small issues before they become problems.
Report faults promptly
If something seems wrong, contact your installer. Avoid changing technical settings yourself, as this can affect performance and may void warranties.
Lower flow temperatures generally improve efficiency, but your settings need to actually deliver enough heat for your home. This balance is part of what we establish during installation and commissioning.
Is a Heat Pump Suitable for Your Home?
Winter performance matters, but it’s just one part of the picture.
Whether a heat pump suits your home depends on a proper assessment: your heat loss, your current heating distribution, the right equipment selection, and appropriate controls. A property-specific survey is far more useful than making decisions based solely on your home’s age or a heat pump’s advertised specifications.
Many homes in North Wales and Cheshire are well suited to heat pumps—including older properties, provided the system is designed correctly. Others may benefit from some improvements first, such as upgraded radiators or additional insulation.
The only way to know for certain is to have your home properly assessed.
Frequently Asked Questions
Do air source heat pumps work when it is snowing?
Yes. Snow in the air doesn’t stop a heat pump from operating. However, if snow accumulates heavily around or on top of the outdoor unit, it can restrict airflow. Keep the area around your unit clear during heavy snowfall, but avoid using sharp tools or hot water to remove snow from the unit itself.
Why are my radiators less hot than they were with a boiler?
Heat pumps typically run at lower flow temperatures than gas or oil boilers. Your radiators may feel cooler to the touch, but this doesn’t mean your rooms are colder. A heat pump delivers warmth steadily over longer periods rather than in short, intense bursts. If your rooms aren’t reaching comfortable temperatures, that’s a different issue worth discussing with your installer.
Is vapour coming from my heat pump normal?
Usually, yes. During defrost cycles in cold weather, you’ll often see steam or vapour rising from the outdoor unit as ice melts. This is a normal part of operation. However, if you see vapour continuously or notice other unusual behaviour, it’s worth mentioning at your next service.
Should I change my heat pump settings during a cold snap?
Generally, no. Weather compensation is designed to automatically adjust your heating as outdoor temperatures change. Manually overriding settings or turning up the temperature significantly can actually make the system less efficient. If your home isn’t staying warm enough during cold weather, contact your installer to review the settings rather than experimenting yourself.
Can a heat pump heat my home if the power goes out?
No. Like any electric heating system, an air source heat pump needs electricity to operate. If you experience frequent power cuts, you might consider battery storage (such as Tesla Powerwall, which we also install) to provide backup power for essential systems.
Do I need to do anything special to prepare my heat pump for winter?
Not really. Ensuring your annual service is up to date before winter is sensible. Check that nothing is blocking airflow around the outdoor unit and that drainage is clear. Beyond that, a properly installed system is designed to handle winter conditions automatically.
Ready to Find Out If a Heat Pump Is Right for Your Home?
Thinking about a heat pump for your home in North Wales or Cheshire? Speak to JM Renewables about your current heating system and what a suitable installation could involve.
We’ll carry out a proper assessment of your property, explain what to expect in terms of winter performance and running costs, and help you understand the practical considerations before you decide.
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