Do Heat Pumps Work in UK Winter? 2026 Cold Weather Performance Data

The 2025-2026 winter delivered the harshest cold snap the UK has experienced in over five years, with overnight lows of -12°C recorded in parts of Scotland and northern England in mid-January. For heat pump sceptics, this was the moment of truth. Did air source heat pumps fail? Did homeowners freeze? The data tells a very different story, and it is good news for anyone considering the switch.

The Big Picture: Heat Pumps Performed Brilliantly

According to data collected from over 15,000 UK heat pump installations by the Energy Systems Catapult and the MCS, the 2025-2026 heating season saw:

• Average seasonal COP of 3.4 across all UK regions (up from 3.1 in 2023-24)
• 97% uptime during the coldest week of January 2026
• Less than 0.5% of systems required emergency callouts during the cold snap
• Just 4% of customers reported any noticeable comfort issues

In other words, the technology that critics dismissed as "unsuitable for British weather" worked exactly as advertised through one of the toughest tests it has faced.

Understanding COP at Low Temperatures

The biggest myth about heat pumps is that they "stop working" in cold weather. The reality is more nuanced — they continue working but become less efficient as outdoor temperatures drop. Here is how modern UK-installed heat pumps performed in the 2025-2026 winter:

Outdoor Temperature	Average COP (2025-26)	Heat Output Ratio	Comparison to Gas Boiler
+10°C	4.8	100%	5x more efficient
+7°C (UK winter average)	4.1	95%	4.3x more efficient
+2°C	3.4	88%	3.6x more efficient
-2°C	2.8	80%	3x more efficient
-7°C	2.4	72%	2.5x more efficient
-12°C (worst case 2026)	2.0	65%	2.1x more efficient

Even at the absolute worst — minus twelve degrees — a modern heat pump still produces twice as much heat per kWh of electricity as a gas boiler does per kWh of gas. The gap only narrows; it never reverses.

How UK Heat Pumps Handle the Cold

Modern air source heat pumps designed for the UK and Northern European climate use several technologies to maintain performance in cold weather. Understanding these features helps explain why the 2025-2026 winter went so smoothly.

1. Inverter-Driven Compressors

Unlike older fixed-speed units, modern inverter compressors can ramp up to 110% capacity in cold conditions. This allows the heat pump to maintain output even when efficiency drops, ensuring your home stays warm.

2. Enhanced Vapour Injection (EVI)

Premium UK-spec models from brands like Mitsubishi (Ecodan), Daikin (Altherma), and Vaillant (aroTHERM plus) use EVI technology to maintain efficient operation down to -25°C. This is essentially over-engineered for the UK climate, which is why performance held up so well.

3. Smart Defrost Cycles

When ice forms on the outdoor unit (around 0°C with high humidity), modern systems use smart defrost based on actual ice formation rather than timed cycles. The 2025-2026 data showed UK units defrosted only when needed, conserving energy.

4. Backup Immersion Heaters

For the rare occasions outdoor temperatures drop below the unit's "balance point" (typically -10°C), most UK systems have a 3-9 kW immersion heater that activates automatically. This kicks in for an average of just 18 hours per year in southern England, rising to 65 hours in Scotland.

Regional Performance Variation

The UK has more climate variation than most people realise. Here is how heat pumps performed across different regions during the 2025-2026 winter:

Region	Avg Winter Temp	Coldest Recorded	Seasonal COP	Backup Heater Hours
South West (Plymouth)	+6.2°C	-3°C	3.8	2 hours
London/South East	+5.4°C	-5°C	3.6	8 hours
Midlands (Birmingham)	+4.1°C	-7°C	3.4	22 hours
North West (Manchester)	+4.5°C	-6°C	3.4	18 hours
North East (Newcastle)	+3.8°C	-9°C	3.2	34 hours
Scotland (Aberdeen)	+2.3°C	-12°C	2.9	65 hours
Wales (Cardiff)	+5.2°C	-4°C	3.7	6 hours

Even Aberdeen — the toughest UK climate for heat pumps — achieved a respectable 2.9 seasonal COP, meaning every unit of electricity produced 2.9 units of heat. The backup heater contributed less than 4% of total annual heat output.

Real Homeowner Experiences

Numbers tell one story; lived experience tells another. We surveyed 1,200 UK heat pump owners after the 2025-2026 winter. The results are illuminating:

• 91% said their home stayed comfortably warm throughout the cold snap
• 87% would recommend a heat pump to friends and family
• 78% reported running costs were lower than expected
• 12% noticed slightly longer warm-up times during extreme cold
• 4% reported any system issues; only 0.8% required engineer callouts

"We were nervous about our first proper cold winter with the heat pump. It just kept working. The house stayed at 21°C even when it was -8°C outside. Honestly, you forget it's there." — Mark T., Sheffield homeowner

The Critical Role of Insulation

Here is the dirty secret of heat pump performance: your home's insulation matters more than the heat pump itself. The data from 2025-2026 makes this crystal clear:

Property Insulation	Seasonal COP Achieved	Annual Running Cost
EPC A or B (excellent)	4.0+	£600-£800
EPC C (good)	3.5	£900-£1,200
EPC D (average)	3.0	£1,300-£1,600
EPC E or below (poor)	2.5 or less	£1,800+

Before installing a heat pump, prioritise loft insulation, cavity wall insulation, and double glazing. Even modest upgrades can dramatically improve your seasonal COP. See our home suitability guide for a checklist.

Common Cold Weather Concerns Addressed

Will my heat pump freeze up?

No. Modern heat pumps are designed to operate down to -20°C or below. The outdoor unit produces ice during defrost cycles, but this is normal and self-clearing. Frozen condensate drains are a rare issue — most installers fit heated drain pipes for UK installations.

What about ground source heat pumps?

Ground source units performed even better in 2025-2026, achieving an average COP of 4.2 across all UK regions. The ground temperature stays at around 8-10°C year-round, so winter performance barely changes from summer.

Do I need a backup heater?

Most UK installations include a small immersion heater for emergency use, but in practice it activates rarely. If you live in Scotland or have a poorly insulated home, ensure your installer includes one and sets the cutoff temperature appropriately.

The Verdict on UK Cold Weather Performance

The 2025-2026 winter was a stress test, and modern heat pumps passed with flying colours. Average seasonal COP of 3.4 across the UK means homeowners are getting 3.4 times more heat output than the electricity input. Combined with the Octopus Cosy tariff for cheap off-peak electricity, running costs are now genuinely competitive with gas — and well below oil or LPG.

If you have been holding off because of cold weather concerns, the data is now in. Heat pumps work in UK winters. With the £7,500 BUS grant still available, there has never been a better time to make the switch.

Next Steps

• Get an EPC assessment to understand your home's thermal performance
• Address any insulation gaps before installation
• Use our size calculator to find the right capacity
• Get quotes from at least three MCS-certified installers
• Consider a smart tariff to maximise running cost savings