Do heat pumps still work in the cold weather? It seems unlikely, but lets get factual, not cynical.
There is a growing interest in both air-source and ground-source heat pumps in the UK.
Despite government incentivisation (in the form of the Boiler Upgrade Scheme), the growth of heat pumps remains slow. 🐌
Aside from the need for costs to come down, better-informed potential buyers are necessary to pump up installation numbers across the UK.
One of the many questions homeowners may have is whether or not heat pumps work in cold weather.
In this guide, we’ll provide an in-depth answer to this question and hopefully leave you with a clearer idea as to whether or not a heat pump is for you.
Ready to make your home more energy-efficient and cut down on your heating bills? Get a heat pump quote today from our trusted partners at Heat Geek here.
Do Heat Pumps Work in Cold Weather?
First things first, yes, heat pumps can generally work in cold weather.
However, this is a broad statement and ultimately, it will depend on the quality of the heat pump and exactly how cold we’re talking about.
But, basically, in short, a chilly but above-zero evening isn’t going to cause your heat pump to shut down.
What’s more, it will also really depend on the type of heat pump, not simply the brand or quality. By that we mean, air source vs ground source heat pumps.
On the one hand, air source heat pumps (ASHPs) can work in temperatures as low as -28°C (although some ASHPs aren’t that durable).
However, ground source heat pumps (GSHPs) can often work at even lower temperatures.
After all, GSHPs persist largely underground where temperatures are often 10 degrees Celsius warmer than on the surface.
Watch Our Air Source Heat Pump UK Case Study in the video below:
As a result, it’s very unlikely that GSHPs would stop operating even when the next Beast from the East strikes.
With all that said, there’s of course a difference between a heat pump working at a low temperature and whether it works well.
Naturally, when the weather is cold out and temperatures get closer to the lowest possible temperature the heat pump will work at, the lower its efficiency will be.
Air Source Heat Pumps and Cold Weather
Since ASHPs are less proficient at dealing with cold temperatures than their ground source counterparts, it’s worth putting more of a microscope on this version of the modern heat pump.
As mentioned, some air source heat pumps will continue to work with temperatures as low as -28°C, which is pretty incredible when you think about it.
Considering the lowest temperature on record in the UK stands at -27.2°C (recorded in Braemar, East Scotland in the early ‘80s), an ASHP with a minimum working temperature of -28°C is very unlikely to ever meet this minimum
However, that’s the best-case scenario for minimum operating temperatures.
The average ASHPs have a minimum working temperature of between -10°C and -20°C.
These are still impressive figures but with an average ASHP, it’s not very unlikely that once in a blue moon, they’d shut down during a sharp cold snap.
The Cold and Heat Pump Efficiency
As touched on, cold weather can impact how efficient a heat pump is.
Overall, heat pumps are substantially more efficient than gas boilers (usually by a factor of three), but once the temperature drops below 0 degrees Celsius, heat pumps start to see a drop in efficiency.
On the one hand, a heat pump working when it’s a few degrees below freezing is likely to remain twice as efficient as gas boilers.
However, as temperatures drop further and further, eventually a heat pump would be no more efficient, less efficient and once it reaches its lowest operating temperature, it would still stop working.
Thankfully, there are steps that homeowners can take to protect their heat pumps against the cold.
Along with ensuring that your heat pump is regularly maintained, you should consider hiring a professional to conceal any exposed pipework (or request that this be done upon installation).
The better protected a heat pump is from the elements, the less of an impact cold weather will have on its energy efficiency.
It goes without saying that paying attention to the working temperature range of a heat pump is important before making a purchase, especially if you live in one of the colder regions of the UK such as northern Scotland or Durham.
If you’re not sure what an acceptable working temperature range is for a heat pump in your region, it’s worth getting in touch with a local heating engineer for advice.
How Heat Pumps Keep Going in Cold Weather
So, what is it about heat pumps that can keep them going in freezing temperatures of as low as minus 20s Celsius?
In order to get to the heart of how they manage this, you also need to understand exactly how a heat pump works.
Heat pumps work by harnessing heat energy from the air or ground (depending on what type we’re talking about) before sending this heat energy indoors to warm the property.
Heat pumps are not totally self-reliant from an energy perspective since they still use some electricity to capture the heat energy needed.
The heat is then pushed through a heat exchanger (a.k.a., evaporator) before a refrigerant is used to absorb the heat.
As the refrigerant evaporates it turns into a gas.
Since the refrigerant is capable of absorbing heat in very low temperatures (again, sometimes as low as the minus 20s Celsius), it allows the process to continue despite it being bitterly cold outside.
Only when the heat pump’s minimum working temperature is reached will it be impossible for the refrigerant to turn into a gas and thus the heat pump will stop working.
As for the remainder of the heat pump process, the gassy refrigerant reaches your property’s central heating system so that it may be used to heat your home.
In the case of an air-to-air source heat pump or a ground source heat pump, the heat will be used to warm the home directly, but if you have an air-to-water source heat pump installed, the warm air will be used to heat up water which can then be distributed to radiators and hot water outlets.
Of course, as the refrigerant cools, it will become a liquid once more.
Frequently Asked Questions
What are the best air-source heat pumps for cold weather?
The very best option is incredible, albeit expensive Daikin Altherma 3 H HT. This air source heat pump can function in temperatures as low as -28°C.
However, unless you’re expecting your region to see the lowest record temperatures in UK history, there are many more affordable ASHPs with a still superb minimum operating temperature of -25°C.
These include the highly efficient Hitachi Yutaki M RASM-4VNE and LG Therma V R32 Monobloc.
Beyond those examples, there are many more ASHPs that can work in temperatures as low as -20°C, which for most homeowners will be more than adequate.
Can heat pumps freeze?
While this is a possibility, your heat pump should automatically activate a defrost mode when temperatures drop.
The purpose of this mode on a heat pump is to prevent ice from accumulating inside the system, which could ultimately cause it to break down.
If it appears that your heat pump has frozen over, this means that something has gone awry causing your defrost mode to stay inactive.
Should this happen, you’ll need to hire a professional. It may turn out that the heat pump’s refrigerant needs topping up or that some sensors inside the heat pump have failed and need replacing.
Of course, there’s a big difference between a heat pump freezing over and one that is covered with ice and snow.
In the latter case, this shouldn’t cause any issues with the internal functioning of the heat pump since the defrost mode would keep it sufficiently warm to keep running.
At what temperatures do heat pumps work best?
Switching our mindset away from the frigid misery of icy November nights to the blossoming warmth of spring and summer, air source heat pumps flourish when the temperature is somewhere between 10-20°C.
Just as efficiency drops once temperatures go below 0°C, heat pumps generally see their efficiency levels decline once temperatures rise above 20°C.
While it will depend on the specific heat pump in question, for the most part, air source heat pumps can continue to operate at temperatures of up to the 40s Celsius.
More heat pump guides:
What about ground-source heat pumps?
Since these heat pumps generally deal with temperatures ten degrees greater than on the surface, it’s important to adjust the figures listed above accordingly.
As a result, the ideal outdoor temperature for a GSHP is more like 0-10°C and the upper limit of many such heat pumps would fall in the 30s Celsius.
However, whether it’s a ground or air source heat pump you’re looking for, the only way to know for sure what temperatures are best for any given heat pump is to look at the specifications of each.
