Flammable (A3) Refrigerants

The publication is currently under development and will be available for viewing on this page at a later date. Subscribe to our newsletter for updates.

Background

The stationary air conditioning (AC) sector is currently the largest source of hydrofluorocarbon (HFC) emissions in California. Its largest subsector, residential AC, accounts for over 60% of the sector’s emissions.

The demand for AC equipment is expected to increase as the climate warms, populations grow, and decarbonization policies increase heat pump (HP) installations to replace fossil-fuel-based heating equipment.

HPs are a key decarbonization tool and rely on refrigerants (in most cases, HFCs) to provide cooling and heating.

Recognizing the need to transition to ultra-low-global warming potential (GWP) refrigerants (GWP <10) while decarbonizing the building sector, the U.S. Department of Energy (DOE) convened a working group with industry stakeholders in 2024 to chart a path for updating safety standards and building codes to allow for the expanded use of ultra-low-GWP refrigerants in AC/HP products.

Flammable (A3) refrigerants (like propane and isobutane) are already widely deployed in domestic refrigeration and some commercial refrigeration applications and are now being used in AC/HP technologies in Europe and Asia. Propane is the refrigerant of choice for newly developed residential “monobloc” air-to-water heat pumps (ATWHPs) in Europe. These ATWHPs operate very similarly to other AC/HP technologies, except that, rather than cooling or heating the air in a building directly, they cool or heat the air indirectly via a distributed water line throughout the building.

The DOE working group identified the need to fully understand the risks of A3 refrigerants in residential ATWHPs as a high-priority project.