ET25SWE0036 - Improving HVAC Refrigerant Charge Value Estimates for Residential Systems

In 2022, greenhouse gas (“GHG”) emissions in California were approximately three hundred seventy (370) million metric tons of CO2 equivalent (“MMTCO2e”) (California Air Resources Board, 2024). Second only to the transportation sector, California buildings account for twenty-five percent (25%) of the annual total (California Law, 2019). One component of the GHG emissions from buildings is leakage of refrigerants from Heating, Ventilation, and Air Conditioning (“HVAC”) systems. During the lifetime of installed HVAC equipment, leakages can occur due to corrosion or faults in piping and pipe connections, mechanical vibrations, physical damage, or simply age-related wear and tear. Leakages can also occur at the beginning of life (leaks while charging the system) and end-of-life, if refrigerant recovery is not executed properly.

To achieve California’s decarbonization goals through electrification, the state is encouraging the replacement of gas appliances with electric ones. This includes the increased installation of HVAC heat pumps, which introduces refrigerants and makes their management more urgent. A recent report (The National Renewable Energy Laboratory (“NREL”), 2022) indicated that refrigerant leakage accounts for fifteen to twenty percent (“15%-20%”) of total GHG emissions (including emissions from power generation) in commercial buildings nationally. In states with a cleaner grid (such as CA) the GHG emission proportion attributable to refrigerant management is even greater.

For California Investor-Owned Utility (“IOU”) programs, avoiding GHG emissions from HVAC system refrigerant leakage has a direct effect on the cost effectiveness of a measure and whether it passes the fuel substitution test, and the refrigerant avoided cost test. The existing measures in the Energy Trading and Risk Management (“eTRM”) measure catalog for residential refrigerant charge values is:

• - Refrigerant Charge Adjustment, Residential (SWSV006-01)
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This measure, as well as new measures that may be proposed for the 2028-2029 program cycle will benefit from a better understanding of refrigerant charge values for estimating leakage rates. This research was proposed by The California Public Utilities Commission (“CPUC”) in the Database for Energy Efficiency Resources (“DEER”) 2026 Resolution (3) and will impact all CA energy efficiency programs offering residential HVAC measures.

TRC Engineers, Inc. (“TRC” or “Implementer”) will provide all qualified personnel from internal staff (the (“Project Team”) to complete this project. The Project Team will collect the most recent refrigerant charge value data from Residential HVAC equipment manufacturers and distributors to improve the reliability of the charge values used in measure development. This project will result in proposed updates to the data tables underlying the DEER Refrigerant Avoided Cost Calculator (“RACC Tool”) and Combined Refrigerant Avoided Cost and Fuel-Substitution Calculators, Version 3.1 (“RACC-FSC_v3.1 Tool”) tools.

The report focuses on updating refrigerant charge values for residential HVAC equipment to improve the accuracy of the Refrigerant Avoided Cost Calculator (RACC) Tools used in California energy efficiency programs. Conducted on behalf of the California Public Utilities Commission (CPUC) and CalNEXT, the study addresses the transition to low-global-warming-potential (GWP) refrigerants, such as R-454B and R-32, mandated by state and federal regulations. These refrigerants replace the high-GWP R-410A, which is being phased out due to its environmental impact. 

The research team collected refrigerant charge data from 19 manufacturers, analyzing 736 systems across various residential HVAC equipment categories. The study identified significant differences in refrigerant charge values based on equipment type, capacity, and refrigerant type. The report recommends updating the RACC-FSC_v3.1 Tool to reflect these findings, including revising residential HVAC equipment categories and refrigerant charge values to improve cost-effectiveness and greenhouse gas (GHG) savings calculations. 

Key recommendations include adopting new residential HVAC equipment categories (Table 3) and updating refrigerant charge values (Table 8) for both low-GWP and legacy refrigerants. The report also highlights the need for more granular data to enhance the accuracy of leakage rate estimates and cost-effectiveness analyses. These updates will benefit California’s energy efficiency programs by providing more accurate data for estimating refrigerant leakage rates and GHG emissions, aligning with the state’s decarbonization and electrification goals. 

The study underscores the importance of accurate refrigerant charge data in achieving regulatory compliance and optimizing energy efficiency measures. It also provides a framework for updating default assumptions and improving the reliability of tools used in energy efficiency programs.