The Heating Capacity Ratio (HCR) is a performance metric that indicates how effectively a heat pump maintains its heating capacity in extremely cold outdoor conditions. It compares the system’s heating output on a very cold day to its output during milder winter temperatures.
Specifically, HCR compares heating capacity at 5°F to that at 47°F, offering a clear picture of how much heat the system can still deliver as the temperature drops.
How Is HCR Calculated?
HCR is calculated using the following formula:
HCR = Heating Output at 5°F / Heating Output at 47°F
A higher HCR means the heat pump is better able to maintain heating performance in cold weather.
Cold Climate Heat Pump & ENERGY STAR Requirements
Heating Capacity Ratio (HCR) is a core requirement for cold-climate heat pump performance standards. Under ENERGY STAR guidelines, heat pumps must meet specific capacity and efficiency criteria to qualify for a cold-climate designation.
To meet these standards, a heat pump must:
- At very cold outdoor temperatures – 5°F, the heat pump must still deliver at least 70% of the heating power it can deliver at 47°F.7
- Maintain a Coefficient of Performance (COP) of at least 1.75 at 5°F, ensuring the system remains efficient even in extreme cold. COP measures the efficiency by comparing heat output to energy input at a specific operating condition.
Why HCR Matters When Choosing a Heat Pump
When selecting a heat pump for a cold climate, HCR is one of the most important indicators of real-world performance. A system with a high heating capacity ratio is better equipped to deliver consistent warmth on the coldest winter days, reducing comfort issues and limiting reliance on backup heating.
