Do heat pumps work in cold weather?

How does a heat pump work in winter?

In winter, a heat pump works by extracting heat from an outside source and transfers it indoors to warm your home. It does this using a refrigerant that absorbs heat from its source (air, ground, or water) and compresses it to increase the temperature. The warm refrigerant then moves through a coil inside your home, releasing heat.

The way a heat pump works isn't dependent on the season. Even in freezing weather, there’s still some heat that the heat pump can capture and use from the outside source.

How efficient are air source heat pumps in winter?

Air source heat pumps remain highly efficient in winter, typically operating at 300% efficiency in temperatures above 0°C. In extremely cold temperatures such as -10°C and below, standard air source heat pumps start to lose efficiency. Luckily in the UK, temperatures in the winter usually range between 2 and 7°C on average so it’s unlikely that the cold weather will affect the efficiency of your heat pump.

How cold can a heat pump get and still work?

Most modern air source heat pumps can work efficiently down to -10°C. They’ll still work below this temperature, just not as well. It's only when you get to temperatures as low as -20°C and below that your heat pump may start having issues.

Meanwhile, water source heat pumps can handle cold conditions—as long as the water doesn’t freeze over. Ground source heat pumps, on the other hand, benefit from the ground’s stable year-round temperature, allowing them to operate reliably even in extreme lows of -40°C.

Can your heat pump freeze in winter?

An air source heat pump can freeze in winter, but they often have defrost cycles to prevent excessive ice buildup. If your heat pump is completely frozen and not defrosting, it may need professional servicing. Since ground and water source heat pumps are tucked away underground or submerged in water they’re naturally protected from the cold, which means that freezing is rare.

How do I know if there's a problem with my heat pump in winter?

Heat pumps are designed to work efficiently during winter, but they can experience issues that affect performance. Recognising early signs of trouble can help prevent bigger problems and costly repairs.

If you notice any of the following issues and they don’t go away, it’s important to contact a qualified engineer to diagnose and fix the problem before it worsens.

A sharp rise in your heating bills

Another warning sign is a sharp rise in heating bills. Although energy bills are higher during the winter months, if your energy costs suddenly spike it might mean the heat pump is overworking itself.

Ice build-up on your air source heat pump

A little build-up of ice is normal, but if the outdoor unit of your air source heat pump is icing up too much, this could be a sign of trouble. Excessive ice suggests issues with the controls, fan, low refrigerant levels, too much heat being removed too quickly or airflow blockages.

Watch for these signs to keep your heat pump efficient all winter. If issues persist, calling in a professional can help prevent costly repairs later down the line!

How to keep your heat pump working efficiently in cold weather

A heat pump is a great way to heat your home efficiently, but during colder months, it requires proper care to maintain its performance.

Insulate your pipes

Insulating the pipes that carry refrigerant and heated water helps prevent heat loss and improves energy efficiency. Proper insulation ensures that heat is retained as it moves through the system. Reducing heat loss allows the heat pump and heating system to be more efficient and keeps your home warmer.

Keep your air source heat pump outdoor unit clear from any debris

For your air source heat pump to work at its best, it will need plenty of airflow. A blocked unit can struggle to heat your home efficiently, leading to higher energy bills and potential damage of the unit. Check it regularly, clear away leaves, snow, and dirt, and trim nearby plants to keep at least two feet of open space around it.

Ensure your home is well insulated

A heat pump performs most efficiently in a well-insulated home, where minimal heat loss allows it to maintain warmth with less energy. Seal gaps around windows, doors, and loft hatch with weather stripping or caulk to minimise heat loss and keep your home well insulated.

Adding loft insulation and wall insulation can further improve energy efficiency, allowing your heat pump to maintain a stable temperature without excessive energy consumption.

Service your heat pump before winter

Having your heat pump serviced before the winter comes around is key. An inspection of the pump and its installation pipework will ensure it’s safe and in line with the manufacturer’s instructions. Catching small issues early by servicing your heat pump helps prevent costly breakdowns when you need heat the most and will keep it working efficiently.

If you have an air source heat pump, our heat pump service plan can help you stay ahead of potential problems and keep your home warm all winter long.

Update central heating pipes and radiators

Upgrading to larger pipework and more efficient radiators can help improve heat distribution. Heat pumps operate at slightly lower temperatures than traditional gas boilers (55 degrees as opposed to 75 degrees) and therefore heat the room more slowly, so correctly sized pipework and radiators will allow the correct amount of heat to be delivered to a room to maintain comfort levels.

Check for system alerts

Many modern heat pumps have built-in diagnostic alerts to notify you of potential problems. Regularly check your system’s display panel or smart thermostat for error codes and system warnings to catch problems early.

Check your air source heat pump’s vents and filters

Clogged evaporators and blocked vents on an air source heat pump can reduce efficiency and airflow, making your heat pump less efficient. Make sure your vents are clear and unblocked and check your evaporator fins regularly to keep them free from dust and debris, as this will help to keep your heat pump running smoothly and efficiently.

Keep your air source heat pump free from ice

As we’ve already touched on, a small amount of frost is normal but excessive ice buildup on the outdoor unit of your air source heat pump can reduce efficiency. If you notice thick ice forming, turn off the power to the heat pump system at the circuit breaker and gently melt using a hot water bottle.

When removing ice from a heat pump it’s important to never use sharp tools, as this can cause damage. If ice buildup persists, it may indicate a faulty defrost cycle, and you should contact a professional to inspect the system.

By following these steps, you can keep your heat pump running smoothly and efficiently throughout the winter, ensuring a warm and comfortable home while keeping energy costs under control.

Common questions about how heat pumps work in winter

Do ground source heat pumps work in winter?

Yes, ground source heat pumps work efficiently in winter because the ground maintains a stable temperature all year round, between 10-16°C on average. This allows them to provide consistent heating without losing efficiency, unlike air source heat pumps.

Do water source heat pumps work in winter?

Yes, water source heat pumps work in winter as long as the water source doesn’t freeze. According to GreenMatch, water source heat pumps are impressively efficient, reaching 300% to 600% efficiency even on the coldest winter days.

Get winter ready and book your air source heat pump service today

Keep your air source heat pump running efficiently all year with a professional service from HomeServe. Regular maintenance prevents breakdowns, improves performance, and ensures your home stays warm when you need it most.

Check out our heat pump service plans and book your service so you can sit back, relax, and feel confident your heat pump keeps you cosy during the colder months.