Why is my heat pump not heating properly in cold weather?
Why is my heat pump not heating properly in cold weather?
Heat pumps lose efficiency in cold weather because they extract heat from outdoor air, and there's less available heat energy when temperatures drop below freezing. This is normal physics, but several factors can make the problem worse than it should be.
Understanding Heat Pump Cold Weather Performance
Air-source heat pumps work by extracting heat from outdoor air and transferring it inside. When outdoor temperatures drop below 5°C (41°F), efficiency begins declining noticeably. At -10°C (14°F), most standard heat pumps operate at only 60-70% of their rated capacity. However, modern cold-climate heat pumps are designed to maintain heating capacity down to -15°C to -25°C, making them suitable for Metro Vancouver's mild winters where temperatures rarely drop below -5°C.
The most common issue is improper sizing or installation. Many heat pumps in Vancouver were sized for cooling loads rather than heating loads, leaving them undersized for winter heating. Your heat pump should be sized to meet 100% of your heating load at the design temperature (typically -5°C for Vancouver). If it's undersized, it will struggle on the coldest days and rely heavily on expensive backup electric resistance heating.
What to know in Vancouver
Metro Vancouver's wet winter climate creates additional challenges. Ice buildup on the outdoor coil is common when temperatures hover around freezing with high humidity. Your heat pump should automatically defrost every 30-90 minutes, but if the defrost cycle isn't working properly, ice accumulation will severely reduce efficiency. Check that the outdoor unit isn't blocked by snow, leaves, or debris, and ensure there's at least 18 inches of clearance on all sides.Maintenance and Performance Issues
Several maintenance issues can worsen cold weather performance. Dirty air filters restrict airflow and force the system to work harder. Low refrigerant levels due to leaks will reduce capacity significantly in cold weather. Faulty thermostats may not be calling for backup heat when needed, or may be switching to backup heat too early, driving up electricity costs.
When to Call a Professional
If your heat pump is running constantly but not maintaining temperature, or if you notice ice that doesn't melt during defrost cycles, contact a licensed HVAC contractor immediately. In BC, heat pump installation and refrigerant work must be performed by Technical Safety BC (TSBC) licensed contractors. Don't attempt refrigerant repairs yourself – it requires specialized equipment and licensing.
Start by checking your air filter and clearing any debris from the outdoor unit.
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