CO₂ vs. A2Ls in Commercial Refrigeration

Regulations 

The primary driver behind the shift from HFCs is legislation aimed at phasing down high-GWP refrigerants. The F-Gas regulation in Europe and the AIM Act in the United States are pushing industries toward refrigerants with lower environmental impact. 

As a natural refrigerant, CO₂ has a GWP of 1, making it an environmentally conscious choice that is effectively future-proof against regulatory phasedowns. Retailers investing in CO₂ systems can be confident in long-term regulatory compliance. While constantly evolving, this technology is well-established and widely used around the globe, particularly in Europe. 

A2L refrigerants — such as R-454A, R-455A, and R-454C — also offer significantly lower GWPs than traditional HFCs (typically below 150), though not zero. Although they comply with current regulatory requirements, more stringent regulations in the future could impact their long-term viability, although this is less likely given their low GWP. 

Installation Costs 

The inherent properties of CO₂ and A2L refrigerants dictate different system designs and installation practices. Operating at much higher pressures than traditional refrigerants, CO₂ systems require specialized, robust components like compressors, condensers, and evaporators, as well as stronger piping like XHP or K65 copper/iron alloy or stainless steel.

In addition, most food retail CO₂ systems operate in a transcritical cycle, meaning the CO₂ moves from a supercritical fluid to a gas without a distinct boiling point. This requires sophisticated control systems to maintain efficiency, especially in warmer climates. 

These specialized components can mean higher installation costs, requiring highly skilled technicians with specific training and certifications in high-pressure systems and transcritical refrigeration. Specialized tools and brazing techniques are needed as well. 

On the other hand, A2L systems come closer to traditional HFC systems in terms of operating pressures and component design, which reduces the transition burden for contractors already familiar with HFCs. However, because A2Ls are classified as mildly flammable, they require adherence to specific safety standards during installation, including proper ventilation, leak detection, and limits on refrigerant charge sizes. Therefore, while they are less complex than CO₂, they still require that installers have targeted training on A2L handling, safety protocols, and charge limitations. 

Overall, initial installation costs for A2L systems are generally lower than those for CO₂, making them an attractive option for some retailers. 

Energy Efficiency 

Energy consumption is a major operational expense for food retailers, making efficiency a critical consideration. CO₂ systems can be highly efficient, particularly in colder climates where transcritical operation is less frequent. In warmer climates, however, managing the transcritical cycle efficiently can be more challenging and may require additional technologies — such as ejectors, parallel compression, or adiabatic condenser coils — to maintain high efficiency. 

A2L refrigerants are less sensitive to ambient temperatures, providing consistent efficiency across climates. They often deliver energy efficiencies comparable to — or sometimes even better than — traditional HFCs, making them a strong contender in terms of operational cost. 

One significant advantage of CO₂ is its excellent heat-recovery potential. The high discharge temperatures can be harnessed to provide space heating or hot water, offsetting other energy costs. 

Safety 

Both CO₂ and A2L refrigerants involve specific safety considerations. For instance, the high operating pressures of CO₂ systems pose a risk if not handled correctly. Proper training, robust equipment, and strict adherence to safety protocols are paramount. In addition, in high concentrations, CO₂ can displace oxygen, posing an asphyxiation risk. Leak detection systems and proper ventilation are essential in enclosed spaces. 

A2L’s mildly flammable classification means these refrigerants can ignite under certain conditions (e.g., in high concentrations with an ignition source). Safety measures include charge limits, leak detection, and ventilation as defined by building codes and industry standards.  

Considerations 

For contractors, the choice between CO₂ and A2L affects both workforce development and day-to-day operations. CO₂ requires a significant commitment to specialized high-pressure and transcritical systems training, as well as specialized high-pressure tools. A2L systems require fewer specialized tools beyond those for HFCs, but still demand proper training for safe handling of mildly flammable refrigerants and adhering to charge limitations. 

Before deciding which course to take, food retailers should assess their regulatory environment, market needs, budget, and long-term operating goals. Contractors can play a key advisory role in guiding retailers through the complexities of each option.  

For retailers seeking a highly future-proof, environmentally resilient solution with heat recovery benefits — and who are prepared to invest in more complex technology — CO₂ is a compelling choice. For those prioritizing a compliant, efficient, and generally less complex transition from HFCs with lower initial costs and consistent performance across climates, A2L refrigerants offer an excellent alternative. 

Ultimately, a collaborative approach between food retailers and knowledgeable contractors, supported by a clear understanding of project requirements, will help ensure the right refrigerant choice for a sustainable and efficient future.