One of the biggest myths surrounding heat pumps is that they stop working properly once winter arrives.
It is easy to see why people think this. The idea of taking heat from cold outdoor air sounds counterintuitive, especially during freezing temperatures.
However, modern heat pumps are specifically designed to work in cold climates. In fact, some of the countries with the harshest winters in Europe also have the highest rates of heat pump adoption. Norway, Sweden and Finland use heat pumps extensively despite winter temperatures that are often far lower than Scotland.
The real question is usually not:
“Do heat pumps work in winter?”
It is:
“Has the system been designed properly for the property?”
That distinction matters far more than most people realise.
Heat pumps continue operating efficiently in cold weather conditions
Modern heat pumps are designed to work efficiently in cold weather and can continue producing heat even when outdoor temperatures fall below freezing. Air source heat pumps extract ambient heat from the outside air and use refrigerant technology to transfer that heat indoors, allowing them to operate throughout winter conditions common in Scotland. System efficiency can reduce during extremely cold periods because the unit must work harder to maintain indoor temperatures, but correctly sized systems with good insulation and suitable emitters can still provide reliable heating. Features such as inverter compressors, defrost cycles, and weather-compensated controls help maintain consistent performance during colder weather.
There Is Still Heat in Cold Air
Even when outdoor air feels freezing, it still contains heat energy.
A heat pump extracts this heat using refrigerant and compression technology, then transfers it into your heating system. This is why heat pumps are able to continue operating even in temperatures below 0°C.
Modern cold-climate systems are capable of functioning in temperatures as low as -15°C to -25°C depending on the manufacturer and system design.
This is also why many experts compare a heat pump to:
“A fridge working in reverse”
Rather than creating heat directly, the system transfers existing heat energy from one place to another.
Most Winter Performance Problems Are Actually Design Problems
When people complain about heat pumps performing badly in winter, the issue is often not the heat pump itself.
It is usually one of these:
- Incorrect system sizing
- Poor insulation
- High flow temperatures
- Undersized radiators
- Poor installation quality
A poorly designed system may struggle because it has been configured to behave like a traditional boiler.
That is one of the biggest mistakes made with heat pump installations.
As many installers now point out:
“A heat pump should not be treated like a gas boiler with a different badge on it.”
Heat pumps operate differently and need to be designed differently from the start.
Air Source Heat Pumps Work Best Using a “Low and Slow” Approach
One of the biggest mindset changes for homeowners is understanding that heat pumps are designed to heat properties differently from boilers.
Gas boilers are built around:
- short bursts of high heat
- rapid warm-up times
- high radiator temperatures
Heat pumps work more efficiently using a steadier approach often described as:
“Low and slow” heating
Instead of rapidly heating a room to high temperatures, the system maintains a stable and consistent indoor temperature over longer periods using lower flow temperatures.
This approach:
- improves efficiency
- lowers electricity demand
- reduces temperature swings
- improves comfort over time
Many homeowners initially think the system is “not as hot” when in reality it is operating exactly as intended.
Why Flow Temperature Matters So Much
Flow temperature is one of the biggest factors affecting winter efficiency.
This is the temperature of the water circulating through your radiators or underfloor heating system.
Most heat pumps perform most efficiently around:
- 35°C to 40°C
As flow temperatures rise:
- efficiency reduces
- electricity demand increases
- COP drops
This is why properly sized radiators and underfloor heating systems often improve heat pump performance significantly.
According to Energy Systems Catapult research, well-designed systems operating around 40°C can still maintain comfortable homes even during colder weather.
Why System Design Matters More Than Climate Alone
One of the strongest arguments against the idea that heat pumps do not work in winter is the fact they are widely used in countries with far colder climates than Scotland.
Norway has one of the highest heat pump adoption rates in Europe despite experiencing significantly lower winter temperatures.
The reason these systems continue performing well is not simply the equipment itself. In most cases, it comes down to:
- correct system sizing
- lower flow temperatures
- good insulation
- properly balanced heat emitters
- installations designed around efficiency rather than boiler-style heating
This is why experienced installers often place far more importance on system design than the brand of heat pump being installed.
We often find older heating systems designed around high boiler temperatures need radiator upgrades before a heat pump can operate efficiently at lower flow temperatures.
Insulation Still Matters
Heat pumps generally perform better in properties that retain heat efficiently.
Good insulation:
- reduces heat loss
- lowers demand on the system
- improves running efficiency
- helps maintain stable indoor temperatures
This does not mean older homes cannot use heat pumps. Many existing properties can still perform very well with correctly designed systems. However, improving insulation and reducing draughts will usually improve overall performance and running costs.
Cold Weather Does Affect Efficiency, But Not in the Way Most People Think
Heat pumps do become slightly less efficient during freezing temperatures because there is less available heat energy in the air.
However, studies show the reduction is often far smaller than people assume.
Research from Energy Systems Catapult found only a marginal decline in efficiency during some of the coldest winter days tested in the UK.
This means:
- a correctly designed system can still operate efficiently
- winter performance remains reliable
- running costs are usually still competitive over a full heating season
Systems designed around lower flow temperatures and efficient heat distribution usually maintain better winter performance and higher efficiency levels over time.
The key factor is nearly always installation quality and system setup.
Final Thoughts
The idea that heat pumps stop working in winter is largely based on outdated systems and poor installations rather than modern heat pump technology itself.
In most cases, winter performance comes down to how the system has been designed. Properties with correct sizing, lower flow temperatures, suitable heat emitters and good insulation can continue heating efficiently throughout colder weather.
This is also why two homes using similar heat pumps can perform very differently in winter. The difference is often not the brand on the wall, but the quality of the design behind it.
As more homeowners move away from oil, gas and direct electric heating, understanding how heat pumps actually operate becomes increasingly important. Modern systems are designed around steady, efficient heating rather than short bursts of very high temperatures, which is why expectations and setup matter just as much as the equipment itself.
For more information about heat pump systems and installation, you can explore our:
- Installation Services for Air Source Heat Pumps
- Air source heat pumps Installer in Aberdeen
- Installation of Air Source Heat Pumps in Aberdeenshire
Or chat to the team for advice on the right setup for your property.
