Laboratory-Based Performance Evaluation of State-of-the-Art Heat Pump RTU for Enhancing Building Energy Modeling

This study presents a comprehensive laboratory-based evaluation of a state-of-the-art 7.5-ton, two-stage heat pump rooftop unit (RTU) equipped with a 36-kW backup electric heater. Testing was conducted at the National Laboratory of the Rockies under a wide array of heating conditions, including both defrost and non-defrost scenarios, to capture real-world operational characteristics. The laboratory setup adhered closely to AHRI 340/360 standards, validating both the test environment and the RTU's rated performance. Detailed steady-state performance results were obtained for various indoor and outdoor conditions, while the effects of on/off cycling, backup electric heating, and defrost operations were systematically measured to assess their impact on overall efficiency and operational behavior. Indoor fan power was also evaluated at different airflow rates. The resulting high-fidelity performance data were used to develop improved heat pump RTU models for building energy simulation tools such as EnergyPlus. These refined models were integrated into the ComStock framework to quantify national-scale energy, cost, and grid impacts associated with widespread deployment of high-efficiency heat pump RTUs in commercial buildings. This work provides both robust equipment data and analytical context necessary for understanding the broader benefits and challenges of transitioning the commercial sector to heat pump RTUs.