Eco Happy (Solar Expert)

Published February 23, 2024

When thinking about heat pumps, the question that pops into most people’s minds is whether they work in cold weather. And the answer is yes, heat pumps can generally work in cold climates. Of course, this is a bold statement, and it ultimately depends on the quality of the pump and just how cold we’re talking about.

It also depends on the type of heat pump, not just the brand or quality. Meaning, it depends on whether it’s an air source heat pump or a ground source heat pump.

How Heat Pumps Work In Cold Weather

Are you curious about how heat pumps manage to keep your home warm and toasty, even when the weather outside is frightful? Well, prepare to have your mind blown, because these eco-friendly heating solutions don’t rely on burning fuel like old-school furnaces.

Instead, they use a nifty little trick: they snatch heat from the outside ground or air (depending on whether it is a ground or air source heat pump), even when it’s chilly, and transport it right into your living room. So, let’s take a peek under the hood and unravel the science behind this wintery wonder.

  1. The evaporator: So, this cold zone is like a heat magnet, and it’s pretty cool (pun intended). Basically, there’s a liquid called refrigerant that flows through the tubes of an evaporator and sucks up warmth from the outside air or ground. And get this, it can even do it at super low temperatures, like -7°C!
  2. The compressor: This part is the muscle of the operation! It’s like a little pump that takes the heat from inside and squeezes it under pressure, making it super hot and ready to be released outside.
  3. The condenser: Welcome to the “heat-sharing hub” – where the magic happens. A pressurised, hot refrigerant flows through the condenser’s tubes and comes into contact with a circulating fluid (usually water). It’s like a match made in science heaven – the heat gets passed from the refrigerant to the water.
  4. The heat exchanger: So, we’ve reached the final destination of our water-heating adventure. This is where the real magic happens. The water, which has now become a heat-borrower, continues its journey to warm up your home’s heating system. And voila! Your living space is now getting warm, giving you a cosy hug that you’ll never want to leave. Isn’t that just amazing?
  5. The cycle repeats: Once the heat is delivered, the refrigerant cools down and heads back to the evaporator, ready to repeat the process and steal more warmth from the outside. It’s a never-ending cycle of heat-snatching and comfort-spreading!

Remember, the colder the outside, the harder the heat pump has to work. That’s why some models have special features like:

  • Variable capacity compressors adjust their power based on the outside temperature, ensuring optimal performance even in frosty weather.
  • Low-temperature start-up kits help the heat pump extract heat even in extreme cold, keeping your home toasty no matter what the thermometer says.

Working temperatures

Let’s chat about heat, hot water pumps and frigid winter weather.

Air source heat pumps (ASHP)

ASHPs or air source heat pumps work in cold weather conditions by transferring heat absorbed from the outside air to an indoor space. It can work in sub-zero temperatures, up to about -20 degrees Celsius, whereafter it will no longer work to heat your home.

Ground source heat pumps (GSHP)

Then, there are ground source heat pumps. These heat pumps are units usually installed inside your home or other buildings and powered by electricity. They are connected to a series of pipes called ground collectors that are laid underground, either in horizontal trenches between 1.5 – 2 metres deep or in vertical boreholes around 100 metres deep.

Ground source heat pumps work at even colder temperatures, and can still heat your home even if it is -40 degrees Celsius outside!

Impact of cold weather on heat pump efficiency

Air source heat pumps (ASHPs) are less efficient in cold temperatures than ground source heat pumps. The lowest temperature on record in the UK is -27.2°C, and while some ASHPs can operate at -28°C, the average minimum working temperature is between -10°C and -20°C. It’s possible for an ASHP to shut down during a cold snap, but their performance is still impressive.

Factors affecting efficiency

Your heat pump’s efficiency is crucial in keeping your home warm and comfortable, even during extreme conditions. Modern pumps have advanced technology to remain efficient in cold weather. Ground-source pumps are ideal for extremely cold regions. High humidity can affect its performance, but advanced dehumidification features can help.

Solar energy can power it directly, lowering costs. Smart control systems adapt to the weather, keeping your home comfy and your wallet happy. Choose the right model and conquer the weather while saving the planet.

1. Temperature of the source (air or ground)

Air source heat pumps have to work extra hard to extract warmth from the frigid air, especially when the temperature dips below their comfort zone. However, ground source heat pumps tap into the Earth’s constant geothermal energy, making their job much easier and more efficient.

2. Temperature desired in the home

Of course, another factor affecting your heat pump’s efficiency is how you control the temperature in your home. If you’re using a new heat pump, it might be a bit slow when reacting to changes you make when compared to a gas or oil heater.

If your home doesn’t feel warm enough, we recommend increasing the temperature by only 1 or 2 degrees via your thermostat or the app of your smart thermostat. It’s also wise to wait about 24 hours to give your heat pump the time to heat your entire home before making additional adjustments.

To control the temperature in each room without putting strain on your heat pump, you can use the thermostatic radiator valves on your radiators (make sure to read our guide on the best thermostatic radiator valves). For your main living areas, we recommend turning up the valves to their maximum setting to ensure that your heat pump works efficiently.

Comparison with Gas Boilers

So you are bundled up under a heap of blankets, shaking with cold while your gas boiler operates noisily, consuming fossil fuels and emitting greenhouse gases. Meanwhile, your friend is enjoying a comfortable and eco-friendly winter thanks to their silent and efficient heat pump, which extracts warmth from the air. Who is more efficient at staying warm during the winter season when it comes to heat pumps vs gas boilers?

Efficiency:  While gas boilers are prevalent and powerful, they’re also outdated. During colder drops in temperature, modern gas boilers can be as much as 90% efficient. Heat pumps, on the other hand, have an efficiency rating of around 300% to 400%, depending on whether they’re air source heat pumps or ground source heat pumps, respectively.

Fuel: Gas boilers are highly inefficient and rely heavily on fossil fuels. This puts a strain on your finances and contributes to climate change, resulting in a significant carbon footprint. On the other hand, heat pumps are incredibly eco-friendly, drawing their heat energy from renewable sources, such as geothermal heat. They provide a sustainable solution for winter heating, making them the ultimate source of energy efficiency.

Winterproofing Your Heat Pump

As winter sets in, the cold weather can be quite uncomfortable. Fortunately, your heat pump is here to the rescue. However, even the most reliable heat pump needs some maintenance during the cold of winter, which is why Eco Happy has some tips for you.

Optimal positioning:

Air source heat pump: When installing an air source heat pump, it’s best to position the unit on the ground outside your property. This minimises the amount of pipework required and makes future maintenance easier. However, be careful of potential hazards caused by ice during the defrost cycle, especially in sub-zero temperatures.

If the unit needs to be installed at a higher level, make sure it doesn’t pose any hazards at head height and is easily accessible for service visits.

Ground source heat pump: As mentioned above, your pump’s loop is buried underground. When installing a ground source heat pump, it is important to consider the location and design of the loop carefully. Horizontal loop systems are usually the most cost-effective option and involve digging shallow trenches where polyethene pipes can be laid at depths of 1 to 2 meters.

Sensors and monitoring:

Keeping your heat pump in good condition is vital to ensure that it functions optimally. Dust can accumulate on the pump’s sensors, which can affect its performance. To prevent this, cleaning the sensors using a brush and vacuum is recommended. Additionally, monitoring the gauges and regularly checking the thermostat and pump display is essential.

These gauges provide important information about the health of your heat pump. Early detection of any issues can help you fix them quickly and ensure that your home stays warm and comfortable.

Installation best practices:

As the colder months approach, you’ll want to ensure that your heat pump is working to perfection so here are some tips to maximise its use:

  • Maintain your thermostat: Regularly adjust your thermostat for peak comfort and efficiency.
  • Inspection and maintenance: Look for wear, leaks, or airflow obstructions. Ensure proper radiator heating and water pressure.
  • Hybrid heating: Utilise backups like oil boilers or gas furnaces for extra winter warmth. Explore hybrid systems with solar energy integration.
  • Clear the snow and debris: To prevent performance issues and mould growth, keep the outdoor unit free of blockages.
  • Monitor for de-icing: Ensure ice buildup doesn’t hamper the pump’s operation and efficiency.
  • Smart tech: Invest in a smart thermostat to learn your schedule and optimize temperature settings for comfort and savings. We’ve compiled a guide on the best smart thermostats to get you started.


How cold is too cold for a heat pump?

Heat pumps are efficient in cold weather, but their performance decreases as the temperature drops. Air-source heat pumps work well down to around -10 °C to -20°C, while ground-source heat pumps are effective even in colder climates.

To determine if a heat pump is suitable for your specific situation, it is best to consult a qualified installer or energy professional.

What is the major drawback of a heat pump system?

In very cold weather, the efficiency of air source heat pump systems can decrease. This is because the heat pump has to work harder to extract heat from the air, which can result in increased energy consumption. To address this issue in regions with consistently cold winters, it might be advisable to have a backup heating system like a gas boiler for extreme cold spells.

Ground source heat pumps, however, offer consistent efficiency as they utilise the Earth’s constant geothermal energy, making them a potentially advantageous option in colder climates.

Should I run my heat pump constantly during the winter months?

Heat pumps operate in cycles to maintain your home’s temperature. Continuous use is not recommended as it can lead to unnecessary energy consumption. Optimise performance by understanding your thermostat and settings, or consult a qualified installer for personalised advice.


As we have discussed, the answer to whether heat pumps work in cold weather is not straightforward. Although the performance of heat pumps is influenced by factors such as the type of pump and temperature, it is evident that heat pumps are a sustainable and eco-friendly option for highly efficient heating, even in freezing temperatures.

Remember these essential tips:

  1. Modern heat pumps can operate effectively in cold weather, with some models working down to -28°C.
  2. Ground source heat pumps are even more efficient in cold climates as they tap into the Earth’s constant geothermal energy.
  3. Compared to gas boilers, heat pumps offer significantly higher efficiency (300% to 400%) and rely on renewable energy sources, making them a sustainable and economical choice.
  4. Proper installation, maintenance, and winterproofing practices are crucial for optimal performance and ensuring your home stays warm and cosy all winter long.

For more information, be sure to contact us at Eco Happy; we can help you choose the right heat pumps for your specific needs and climate.

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