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How to Use a Heat Pump in Winter

Becky Mckay
By: Becky Mckay
Updated: 5th November 2021

Cartoon Air Source Heat Pump In Winter

Air source heat pumps are one of the most efficient ways to heat your home all year round.

Even in temperatures as low as -25°C, in some cases, an air source heat pump can continue to heat a property using the air outside. To get the most out of them during the winter, there's a few things you'll need to bear in mind, which we'll take you through in the article.

How heat pumps work

Air source heat pumps extract heat from the air outside and use it to provide central heating, even during the winter.

The air source heat pump itself includes a fan that rotates to bring in the outside air and is installed outside. Once the fan brings in the air, the heating process begins:

  • Outdoor air passes over an exchanger coil which contains a refrigerant fluid
  • The refrigerant fluid boils and evaporates, turning into a vapour
  • That vapour is then compressed at high temperatures to produce heat

Choosing to heat your home with an air source heat pump comes with many benefits:

  • Highly efficient performance
  • Reduced energy bills
  • Payments through the Renewable Heat Incentive (RHI)
  • Lengthy lifetime of up to 25 years
  • Simple maintenance

Air source heat pumps are also able to perform year round but extra attention might need to be paid to the system to get the most out of it during the winter.

How a heat pump works in cold temperatures

It's no surprise that air source heat pumps perform at their best during warmer weather. This is because there's more heat in the air to extract and use to heat the rooms of a home.

With the temperature sitting above freezing, an air source heat pump has the potential to meet all demands for heating and hot water. However, lower outdoor temperatures can mean a lower heat output from the heating system and it can be a good idea to have a back-up heating system. This is where hybrid heating systems come in.

A hybrid heating system pairs a renewable heating system, such as a heat pump, with a traditional boiler. While heat pumps can be used all year round, they're most effective during the summer months. During the winter however, a boiler would be more efficient.

Hybrid heating systems intelligently switch between these 2 heating systems depending on which would perform most efficiently at that time.

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How to use a heat pump in winter

As cold as it might feel outside during the winter months, air source heat pumps are still able to use it to generate heat for your property's central heating system.

These 7 tips will help you to get the most out of your air source heat pump during the winter.

Don't cover the heat pump

It could be tempting to prevent the heat pump from freezing over by covering it but this is something you shouldn't do.

By covering an air source heat pump, the airflow is being blocked which will reduce efficiency and could even lead to mould. The defrost mode will help to keep the heat pump from freezing.

Get a smart thermostat

A smart thermostat is a valuable addition to any central heating system, not only when a heat pump is involved. Having a smart thermostat will give you greater more convenient control over the central heating, which will help in keeping your energy bills down.

Clear leaves, snow and other debris

Much like covering the heat pump, if the area around it is full of leaves, snow or other debris then the airflow will be blocked and the efficiency of the heat pump will begin to drop. So it's important to clear the area around your heat pump as often as possible.

Make sure your home is well insulated

A heat pump can be efficiently heating your home but if the property isn't well insulated then that heat will escape, meaning that you'll only have to heat the property for longer, increasing your energy bills.

Switch to a cheaper energy supplier

Air source heat pumps need electricity to function which can be expensive. While an air source heat pump can perform at efficiencies of around 300%, switching to the cheapest tariff available will keep your bills down to a minimum.

Consider larger radiators

The water heated for circulation around the heating system by an air source heat pump doesn't reach temperatures as high as water heated by a boiler. For this reason, radiators with a larger surface area or underfloor heating are the best heating systems when using an air source heat pump.

Arrange a service ahead of winter

Getting your air source heat pump looked over by a fully-qualified professional ahead of the winter months will ensure that it's running effectively and efficiently when you'll be needing it the most.

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Heat pump problems in winter

Winter is the worst time of year to experience problems with your air source heat pump so if you notice any of the below, contact a heating engineer right away:

Cold air through vents

Air-to-air heat pumps heat the home by blowing warm air through vents but during the winter they can perform more like air conditioning system, blowing cold air through the vents.

The first thing to check is that your air source heat pump isn't on a 'cool' setting. If it isn't then the refrigerant liquid that circulates around the pipes might be leaking. In this case, an engineer will be needed to repair the leak.

Heating bills on the rise

There's a good chance the heat pump will need to use the defrost mode during the winter which means that you'll be getting less heat from your central heating system for every unit of electricity.

This is one reason why you might want to consider installing an air source heat pump as part of a hybrid heating system.

Heat pump has frozen

In the very worst case scenario, air source heat pumps can completely freeze over. The defrost mode should prevent this from happening but if it doesn't then.

Heat pump runs constantly in cold weather
An air source heat pump that's running constantly during the cold weather is nothing to be concerned about as they do run for longer periods than traditional heating systems. Especially during the winter when the heat pump has to run a defrost mode to prevent freezing too.

How to defrost a heat pump

During the winter months, you may well see a thin layer of frost on the air source heat pump but this is nothing to worry about. It only becomes a concern when ice begins to build-up on the coils.

Air source heat pumps have a defrost mode which will help to remove small amounts of frost – you may need to turn the fan on for defrost mode to work. During defrost mode, the heat pump won't be able to generate heat for your property's central heating.

It's important not to use antifreeze to thaw out a heat pump as this could end up causing damage to the system. The defrost mode should be enough to prevent the system from freezing.

It's a good idea to keep the area around the heat pump free from snow, ice and other debris. A quick sweep every now and then will help to keep the heat pump running at its optimal performance.

Should your air source heat pump stop working during cold weather, we highly recommend contacting a qualified engineer who will be able to diagnose and repair the issue.

When is it too cold for a heat pump?

Each air source heat pump model has its own unique features and for winter operation with a key one to note being the minimum operating temperature.

With many models of air source heat pump able to perform in temperatures as low as -20°C to -25°C, there isn't much to worry about here in the UK.

Manufacturer Model Minimum Operating Temperature Maximum Hot Water Temperature
Daikin Altherma 3 -25°C 65°C
Nibe F2040 -20°C 58°C
Samsung EHS Mono -25°C 46°C
Vaillant aroTHERM -20°C 63°C
Viessmann Vitocal 300-A -10°C 65°C
Grant Aerona -20°C 43°C
Mitsubishi Ecodan QUHZ -15°C 65°C
LG THERMA V R32 -25°C 65°C
Hitachi Yutaki S80 -20°C 80°C

Alternatives to an air source heat pump

Underground temperatures are less variable than outdoor air temperatures, which is why, if you have sufficient garden space available, then a ground source heat pump might be the better option.

Using a series of pipes circulating a refrigerant fluid, ground source heat pumps extract underground heat, where the temperature sits at between 10-15°C all year round.

The only downside to ground source heat pumps is the amount of space they need. Not only in terms of the area the pipes will take up but also enough for the vehicles and equipment needed to dig up the ground during installation.

Free heat pump quotes

If you're looking to make your home heating system more renewable this winter – and all year round – then an air source heat pump is a highly efficient solution.

Take a couple of minutes to complete our simple online form and you'll get free quotes from up to 3 heat pump installers based near you. Comparing multiple quotes gives you the greatest chance of finding the most competitive price, significantly more so than accepting the first quote you receive.

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Becky Mckay

About the author

Becky Mckay

Becky is one of our home heating and renewable energy experts and has a wealth of experience writing about the world of heating.

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