How does a heat pump work in winter?

If you’re looking to upgrade your heating system to heat pumps, you’ll no doubt be asking: “do heat pumps really work in cold weather?”. 

The short answer: absolutely. Air to water heat pumps will work in harsh winters, some at temperatures as low as -25 degrees Celsius. Read on to learn how heat pumps work in winter and tips on how to maintain your air to water heat pump during UK winter months.

Do heat pumps work in cold weather?

As heat pumps use fresh air from outside to heat your home, it’s natural to wonder how your home stays warm with a heat pump even in the winter. 

Just because it’s cold, doesn’t mean there isn’t free energy available. Your heat pump uses free energy from the outside air to heat your pump’s refrigerant, which immediately starts boiling, even at subzero temperatures, meaning there’s little to no chance of the refrigerant in your heat pump freezing over, even in the coldest of winters. 

This means your heat pump works exactly the same way in winter as it does the rest of the year – leaving your home cosy and warm for a fraction of the energy cost.

Air source heat pumps: how efficient are they in winter?

Your heat pump system can still warm your home effectively in cold weather. As you’d expect, a heat pump will have to work harder and use more electricity in icy spells, so your efficiency will decrease a little – but heat pumps are still drastically more efficient than traditional heating systems like gas boilers.

When measuring a heat pump’s efficiency in winter, it’s worth looking at Seasonal Coefficient of Performance (SCOP) which gives a zoomed-out view of how a heat pump will perform seasonally. 

The SCOP factors in the temperature changes between summer and winter, to give you a clear picture of efficiency. An Aira Heat Pump, for example, can achieve a SCOP of up to 4.7, meaning it can deliver up to 4.7 kilowatts of heat for every 1 kilowatt of electricity it consumes, making its efficiency over 400%. Beat that, boilers – which struggle to reach even 90% efficiency in moderate weather.

Overall, an air to water heat pump or ground source heat pump is amongst the most efficient home heating systems you could choose, even in the depths of winter – and definitely more efficient than a gas-guzzling boiler.

How cold can a heat pump work?

The coldest temperature at which your heat pump can work depends on both the type of heat pump you have and how effective your home’s insulation is. 

Most households choose an air-to-water heat pump, which still works effectively in temperatures as low as -10C, and some even have an efficiency rate of over 200% at -20C, according to research from Oxford University’s Environmental Change Institute. 

With average UK winters hitting just below 0 degrees, you’ll find an air to water heat pump can keep you cosy on the harshest of winter nights. 

Still don't believe us? Just look to Scandinavia, where heat pumps have been keeping homes cosy for decades. And they're no strangers to sub-zero winters! 

What problems can an air source heat pump face in cold UK weather?

While not as cold as Scandi winters, the UK can face some bracingly harsh weather. For British homeowners with heat pumps, it’s worth bearing in mind that there are certain precautions to take with heat pumps so that they remain as efficient as possible during the worst of the weather.

Learn how to prepare your heat pump for winter.

Can heat pumps freeze up in winter?

Heat pumps can freeze in the winter, but only when the heat pump evaporator is colder than the surrounding air. Should you worry about this happening? Not at all. 

You can prevent your heat pump from freezing up in the winter by ensuring your heat pump is free from leaves and debris and other airflow-blocking items.

How to defrost a heat pump in winter

Spotting frost around your heat pump? Don’t panic. Most heat pumps – including ours – have an inbuilt defrosting setting which will automatically clear up the fans, preventing damage and ensuring they can still work efficiently in heating your home on icy days.

Is it worth getting a cover for your heat pump in winter

A heat pump cover is intended to protect your device from snow and other winter elements. However, in the UK, there is not enough snow for this to be a true concern. 

If you do live in a snowy climate, you may want to consider installing a custom-built cover that is specifically designed for heat pumps, otherwise you could inadvertently block the airflow. Alternatively, inform your installers and they will raise the heat pump off the ground to add some clearance from the snow.

How to make a heat pump more efficient in winter

There are certain precautions a homeowner should take to ensure that their heat pump is not damaged or less efficient during the winter. 

This includes regular maintenance on the pump and servicing (covered when you switch to Aira) to ensure that the air filter is clean and replaced when necessary. 

Your heat pump’s airflow should also be checked to ensure it’s clear from leaves and debris. And, while you may be tempted to play around with your system's temperature, it's best to leave it at a consistent setting to keep it running as efficiently as possible.

Do ground source heat pumps work in winter?

A ground source heat pump is often the most efficient choice of heat pump for extremely cold climates, and will work year-round. 

Why? Because the temperature underground is stable, ranging from 5 to 15 Celsius over the year. This means more heat can be generated using less electricity. 

As a result, you’ll find a ground source heat pump typically has a SCOP of 4 or 5, meaning they can deliver an impressive 4-5 kilowatts of heat for every 1 kilowatt of electricity they consume, making their efficiency 400-500%. Many ground source heat pumps can keep working at temperatures as low as -28 Celcius too.

Are heat pumps worth it in cold climates?

Are heat pumps worth it compared to boilers even in the winter? Absolutely. Boilers need extensive insulation and are often hugely inefficient and guzzle greenhouse gases, as well as requiring regular servicing. 

Heat pumps, however, are 4X more efficient than boilers, meaning you spend less on energy for the energy produced – and your trusty heat pump will be heating your home at a low cost and high efficiency, even in cold weather. 

Take a look at our in-depth comparison of air source heat pumps vs gas boilers to see which system is right for you.

Why choose Aira to provide my heat pump?

Before installing your new heat pump, Aira will conduct a free home energy assessment and custom design to ensure your system is tailored to your home and hot water needs. 

Our best-in-class Aira Heat Pump is not only one of the quietest on the market but uses an R290 refrigerant, a natural refrigerant that provides a higher flow temperature without harming the ozone layer.

If you're still unsure, find out exactly how much a heat pump costs to see if it's right for you.