Do Air Source Heat Pumps Work in Winter? The Truth About Cold-Weather Performance

It’s a fair question and one of the most frequently asked. The idea of relying on outside air to heat your home in January sounds counterintuitive. But here’s the truth: a modern air source heat pump is designed to deliver reliable heating even when the mercury drops well below freezing. In this guide, we’ll explain exactly how these systems keep working in cold weather, what affects their efficiency, and how to make sure yours is set up for maximum comfort and cost-effectiveness all year round. By the end, you’ll know whether a heat pump is the right choice for your home.

How Heat Pumps Perform in Cold Weather

A quality air to water heat pump doesn’t just survive winter, it’s built for it. Modern heat pump systems can still extract usable heat from the air in temperatures as low as -25°C, making them a solid choice for UK homes all year-round.

The secret lies in the refrigerant cycle. The refrigerant inside your heat pump evaporates into gas, even in sub-zero temperatures. That means cold air holds enough energy for the system to absorb to start the cycle. The air starts the process of the refrigerant evaporating into a gas to then be compressed. The compressed refrigerant generates heat for your home’s radiators, underfloor heating, and hot water cylinder.

In typical UK winter conditions (0°C to 7°C), most units maintain a COP (Coefficient of Performance) of between 2.5 and 3.5. Put simply, for every unit of electricity used, you’re getting 2.5–3.5 units of heat, which is far more efficient than gas or electric heating.

If you want to see exactly how an installation works and how the setup affects performance, our Essential Guide to Air Source Heat Pump Installation walks you through the process step-by-step.

Factors That Affect Winter Efficiency

Not all air source heat pumps perform the same in winter. The difference between a system that keeps your home toasty and one that struggles comes down to a few key factors:

1. Choosing a well-made high performing heat pump. A well-made heat pump is designed to work reliably in extreme conditions. That is why they are popular in cold extremely cold places such as Canada and Scandinavia.

2. Insulation Quality. Good insulation means less heat loss, so your pump doesn’t have to work as hard. This will be the same for any heating system; a gas boiler will burn more gas in a poorly insulated home. Less insulation means more energy needed to warm the space regardless of heat source. Where possible it is a good idea to increase insulation. Heat pumps will still work in houses with less insulation, but a bigger system will be needed.  

3. Correct Sizing. An undersized unit will constantly run to meet demand, while an oversized one can cycle inefficiently. An MCS-certified installer will size your system for your exact heating and hot water needs.

4. Smart Controls & Weather Compensation Modern controllers automatically adjust heat output based on outdoor temperatures, improving efficiency during cold snaps.

Want to know if your home ticks the right boxes? Our guide, Is an Air Source Heat Pump Installation Right for Your Home?, covers it in detail.

Maximising Winter Performance

If you’re going to invest in an air source heat pump, you want it running at its best, especially when it’s cold outside. Here’s how to get maximum performance in winter:

1. Set Steady Temperatures. Unlike boilers, heat pumps work best running consistently, not being turned on and off. Keep a consistent target temperature for warmth and efficiency.

2. Maintain Your System. A yearly service ensures your pump is clean, leak-free, and performing as it should during peak heating months.

3. Avoid cold spots. Understandably sometimes people only heat part of the home and turn off radiators in rooms they do not use. By doing this it creates cold spots which suck out heat from the heated areas. This can lead to more work for the heating system rather than reducing energy use.

For more on designing a system that works perfectly for your property, see our Air Source Heat Pump service page.

Conclusion: Winter Is No Obstacle

The idea that air source heat pumps can’t handle a UK winter is one of the biggest myths out there and now you know it’s simply not true. With the right system design and a professional installation, a heat pump will keep your home warm, your water hot, and your energy bills under control, even when it’s freezing outside.

If you want a low-carbon, cost-efficient heating solution that works all year round, it starts with expert advice and a tailored plan for your home.

Don’t guess! Get the facts for your property. Book your free survey with Puraflow Renewables today and discover how an air source heat pump can work for you this winter and beyond.