Heat pumps are praised for their energy efficiency, but when freezing weather hits, they can sometimes underperform. Understanding why this happens is key to keeping your home warm and your heating system running smoothly. Here’s everything you need to know about common cold-weather issues and how to overcome them.
Why Do Heat Pumps Struggle in Freezing Weather?
Installation Mistakes That Limit Performance
Incorrect or inadequate installation is one of the most common reasons heat pumps fail to perform well in cold conditions.
Key installation issues include:
- Wrong unit type: Standard heat pumps aren’t built for sub-zero temperatures. Cold-climate models include enhanced compressors, improved coils, and smarter defrost systems.
- Improper sizing: An undersized unit can’t meet heating demands, while an oversized one may short-cycle, reducing efficiency.
- Poor placement: Outdoor units should be clear of snow and shielded from wind, without blocking airflow.
- Leaky or undersized ductwork: These can seriously affect heat delivery.
- Low refrigerant charge: This limits heating capacity and strains the system.
Solution: Always choose a qualified, experienced installer who carries out a full heat loss calculation and follows manufacturer guidelines for cold-climate installations.
Frozen Coils and Ice Buildup
When extracting heat from freezing air, moisture can condense and freeze on the outdoor coil. This restricts airflow and makes heat transfer difficult.
Signs of this issue include:
- Reduced heating output
- Ice visible on the unit
- Longer heating cycles
Defrost cycles temporarily reverse the system to melt the ice, but frequent defrosting reduces efficiency.
Tips to reduce icing:
- Clear snow and debris around the unit
- Ensure proper drainage under the system
- Avoid obstructing airflow with covers or fences
Clogged Air Filters Reduce Efficiency
Dirty filters can cause major cold-weather issues:
- Poor airflow reduces heat exchange
- The system runs longer, using more energy
- Ice can form on indoor coils due to restricted air movement
Maintenance tips:
- Check filters monthly in winter
- Replace or clean every 1–3 months
- Use manufacturer-recommended filter sizes and types
Keeping filters clean is one of the simplest ways to maintain winter efficiency.
Ageing Equipment and Worn Components
Older heat pumps naturally become less efficient over time. Common wear issues include:
- Compressor fatigue: It takes more power to generate heat
- Coil degradation: Corrosion reduces heat absorption
- Refrigerant leaks: Even small losses impair heating
- Outdated systems: Older models lack smart controls or variable-speed motors
When to act:
- You notice rising bills without changing usage
- The system runs constantly or heats poorly
- You experience frequent breakdowns
Solution: Schedule annual servicing and consider upgrading to a newer, high-efficiency heat pump with cold-climate features.
Reversing Valve Malfunctions
The reversing valve allows your heat pump to switch between heating and cooling. In freezing weather, a faulty valve can lock the system in cooling mode.
Warning signs:
- Blowing cold air during heating mode
- Loud clicking or humming when changing modes
- No temperature response when switching settings
Professional help is essential. Reversing valve issues require diagnosis and repair from a qualified engineer.
Poor Insulation Makes Heating Harder
Your heat pump’s performance is directly affected by how well your home retains heat.
Insulation problems can cause:
- Heat loss through walls, roofs, or floors
- Cold air entering through gaps
- Overworked systems and higher energy use
Ways to improve insulation:
- Top up loft and cavity wall insulation
- Draught-proof windows and doors
- Install heavy curtains or thermal blinds
- Use door seals and letterbox brushes
Better insulation eases the load on your heat pump and makes your home more comfortable year-round.
Thermostat Settings and User Habits
User behaviour can also affect how well a heat pump works in the cold.
Common mistakes:
- Frequent temperature changes: Causes unnecessary system strain
- Blocked vents: Reduces airflow and room comfort
- Neglecting auxiliary heat settings: Can lead to excessive energy use
Smart practices:
- Use a programmable thermostat for consistent heating
- Set realistic temperatures (e.g., 18–21°C)
- Avoid blocking vents with furniture or curtains
- Understand when and how your backup heat system activates
Good habits go a long way toward getting the best from your system in winter.
Need help with your heat pump in Norwich or Norfolk this winter?
Norfolk Renewable Heating provides expert support, servicing, and installation for heat pumps in cold climates. Call us on 07824 393403 or 07939 979217, or fill out our contact form to speak to our team today.
