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16 January 2024

Do heat pumps work in cold weather?

An air source heat pump outside a home in the snow
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How does a heat pump work in winter?

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 other home heaters.

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. Your Vaillant air source heat pump provided by Aira can achieve a SCOP of up to 5.03, meaning it can deliver up to 5.03 kilowatts of heat for every 1 kilowatt of electricity it consumes, making their efficiency over 500%. 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 your heat pump can work will depend 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.

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

It’s no secret that the UK can face some bracingly harsh winters. Heat pumps are still a great choice even for the coldest spells – just ask Scandinavian countries facing even colder winters, who’ve adopted heat pumps in droves. 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.

Can heat pumps freeze up in winter?

Heat pumps can freeze in the winter, when the heat pump evaporator is colder than the surrounding air. But should you worry? 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, one could 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 for home heating) 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 thermostat, try to keep it at one setting to keep it running as efficiently as possible – which is good for the environment and your pocket.

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, meaning they can deliver an impressive 3-4 kilowatts of heat for every 1 kilowatt of electricity they consume, making their efficiency 300-400%. 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. 

Why choose Aira to provide my heat pump?

When you choose Aira to provide your heat pump, you’ll receive installation and necessary parts & servicing with the Aira comfort guarantee that’ll keep you warm all winter long. When installing a new heat pump, Aira will conduct a custom survey and design to ensure your new heat pump is a home heating hero, using best-in-class Vaillant aroTHERM heat pumps. Not only are these amongst the quietest on the market, but they have an R290 refrigerant, a natural refrigerant providing a higher flow temperature without harming the ozone layer.

Contact us for a no-strings chat about improving your home’s energy efficiency!

Heat pumps can provide effective heating in temperatures as low as -25 degrees celsius. And because your package includes our Aira Comfort Guarantee at no extra cost, you’re guaranteed 20 degree celsius cosiness on even the coldest day of the year – or we’ll come straight out to fix it.

An air source heat pump is a sealed unit designed to withstand all weather conditions.

Our Aira Comfort Guarantee promises heating up to 22 degrees, even on the coldest day of the year. 

After switching to a heat pump, you will have the same hot water temperature in your home as before.


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