Low GWP Refrigerant Guide: What Food Retailers Should Know

(Updated March 2025)

Those who can remember the 1990s, when the depletion of the ozone layer led to the phase-out of CFC refrigerants, may be experiencing déjà vu as the food retailing industry is on the cusp of yet another refrigerant transition.

Just as CFCs were replaced by HFCs in the past, we are now on the brink of replacing HFCs due to their high global warming potential (GWP), which contributes significantly to climate change. While HFCs were once hailed as a solution to ozone depletion, their negative impact on the environment has led to the development of new refrigerants that are more sustainable and have much lower GWP.

“HFCs are on the hit list,” says Steve Moss, Head of Refrigeration at City Facilities Management. “This means their days are numbered, and their number will be up before we know it.” Steve expects a faster transition from HFCs than the transition we saw in the 1990s from ozone-depleting CFCs after the Montreal Protocol called for their eradication. “We’re in a fast-tracked phase-down,” he adds. “It’s not going to take 15 years for HFCs to phase out.”

As we look to the future, the debate has shifted between two primary contenders for replacing HFCs in supermarket refrigeration: HFOs (hydrofluoroolefins) and natural refrigerants, like ammonia (NH3), carbon dioxide (CO2), and propane (R290). HFOs, with their lower GWP and ability to be retrofitted into existing systems, have emerged as a leading choice. However, natural refrigerants, rebranded as more environmentally friendly alternatives, offer the benefit of ultra-low GWP values. Yet, the question remains: are natural refrigerants or HFOs the best long-term solution for supermarkets? In this article, we will explore these options and help clarify what supermarkets need to know as they navigate this new refrigerant landscape.

Before we take on this big question, let’s take a step back and define Global Warming Potential for those of us who need a little refresher.

What Is the GWP of a Refrigerant?

Greenhouse gases warm the earth by trapping energy so that it can’t escape the atmosphere, acting almost as a blanket over the earth. CO2 is a greenhouse gas, a very common one produced by both natural processes, such as the decomposition of dead trees, and human activities, such as the extraction and use of fuels like coal, oil, and natural gas.

Global Warming Potential, or GWP, is a measure of how much heat is absorbed (trapped) by specific greenhouse gases in the atmosphere. GWP numbers indicate how much energy will be absorbed by 1 ton of a gas (such as refrigerants, hydrocarbon combustion products, methane from the digestive systems of cows, and many others) over a certain period of time, usually 100 years, compared to the heat absorbed by 1 ton of CO2 (the reference gas).

A gas can be low GWP because it traps less heat or because it breaks down quickly once released into the atmosphere and so has a short lifetime. As refrigerants are the gas of interest here, the higher the GWP of a refrigerant, the greater the warming effect will be on the earth compared to C02. This is why low GWP refrigerants are more environmentally friendly and why businesses that use refrigeration are being required to adopt new lower GWP refrigerants.

The Transition to HFOs in Grocery Stores

New international agreements and state and national laws regulating the release of harmful greenhouse gases, including refrigerants, have been proliferating over the past two decades and started a slow but now accelerating phase-out of high-GWP refrigerants. The American Innovation and Manufacturing (AIM) Act of 2020 included provisions that allow the EPA to phase down and then phase out the use of high-GWP HFCs even faster.

In the U.S., new refrigeration systems that use high-GWP HFCs (such as R404A, the most common refrigerant in use today in the U.S. food retailing industry) can no longer be manufactured or installed. And in California, as of January 1, 2025, California’s Senate Bill No. 1206 prohibits the sale of  the sale of virgin, bulk hydrofluorocarbon (HFC) refrigerants with a global warming potential (GWP) of 2,200 or greater — impacting refrigerants such as R-404A and R-507.

Even elsewhere, national regulations and international agreements restricting the manufacture of new high-GWP refrigerants are reducing their availability and increasing their cost, which will result in the nearly complete elimination of R-404A, R-407A&C, and other common refrigerants over the next 15 to 20 years.

“In existing refrigeration systems across the U.S., CFCs like R-22 and HFCs like R-404A and 407A are being replaced with HFOs and HFO blends,” Steve explains. HFO blends are essentially a mix of a lot of HFO with some HFC refrigerant.

With zero ODP (ozone depleting potential) as well as low GWP, HFOs are considered to be the current best environmentally friendly replacement for HFCs and HCFCs in existing refrigeration systems.

HFO Refrigerants vs. “Natural” Low GWP Refrigerants

While HFOs have been considered the leading low GWP alternatives to HFCs, natural refrigerants are also gaining significant traction, particularly as supermarkets and other industries aim for even lower environmental impact. Here’s a deeper dive into the various refrigerants being considered and their current standing:

HFOs and HFO blends

HFOs are often touted as the leading low GWP alternatives to HFCs due to their relatively low GWP values and their chemical structure, which is less damaging to the ozone layer.

Low GWP refrigerant list

The most common HFOs used in supermarket refrigeration, most commonly used as replacements for R-404A and R-134A,  include:

• R-448A
• R-449A

These offer lower GWP and good energy efficiency and are often seen as “drop-in” replacements, meaning they can work with existing systems with little modification.

R-513A (an HFO blend replacement for R-134a, not R-404A) is another option used in some supermarket applications and offers lower GWP compared to R-448A and R-449A.

To give an idea of how they compare in GWP: R-404A has a GWP of 3943, whereas R-448 has a GWP of 1,273 (67% lower) and R-513A a GWP of 572—about 60% lower than R-134a and 85% lower than R-404A.

Pros:

• Lower GWP than HFCs (R-448A and R-449A have a GWP of ~1300, compared to R-404A’s GWP of ~3922).
• Good energy efficiency, which helps reduce operational costs.
• Mild flammability compared to natural refrigerants

Cons:

The new HFO refrigerants approach the GWPs of some natural refrigerants — and in some instances boast even lower GWPs. But to do so, they take on some of the negative characteristics of natural refrigerants that caused them to fall out of use in the first place.

• Mild flammability (though much lower than other refrigerants like propane): “While it takes a lot more energy to ignite HFO gasses compared to propane, one of the natural refrigerants being promoted today,” says Steve, “their mild flammability has slowed their adoption, as they have not yet been fully approved in building code regulations in most states.”
• Require some training for handling due to flammability

What about HFO blends? The GWP of HFO blends declines to even lower values as the amount of HFCs in the blend is lowered. However, there are drawbacks — the very low GWP HFO blends have some of the same shortcomings as the natural refrigerants — flammability, toxicity, and increased refrigeration system cost or complexity. Take R-1234yF, sold under the brand name Option YF and SOLSTICE-yf, as an example. R-1234yF has a GWP of only 4 but contains small amounts of carbon tetrachloride, which is a potential carcinogen.

Natural refrigerants

Natural refrigerants are gaining momentum, particularly in European markets and supermarkets with more aggressive sustainability goals. The “natural” aspect of these refrigerants is a major selling point, as they have very low to zero GWP and are often viewed as more sustainable choices. These include:

• Ammonia (NH3): A highly efficient refrigerant with near-zero GWP and a long history of use in industrial refrigeration, ammonia has been somewhat avoided due to its toxicity and flammability, but improvements in system design and safety protocols are making it more viable.
• Carbon Dioxide (CO2, R-744): CO2 is a non-toxic, non-flammable refrigerant with an extremely low GWP of 1. It’s already in use in many supermarkets, particularly in Europe, and is growing in popularity in North America, particularly in California. CO2 systems, however, are complex and require more energy in hot climates.
• Propane (R-290): Propane is a natural refrigerant with an incredibly low GWP (3), and it’s being used increasingly in smaller refrigeration systems, like display cases and cold storage. However, its flammability is a concern in large systems.

Pros:

• Ultra-low GWP (e.g., CO2 GWP = 1, propane GWP = 3).
• Long-term sustainability, as they don’t contribute to ozone depletion or global warming
• High efficiency (particularly with ammonia and CO2)

Cons:

• Ammonia: Toxicity and flammability concerns, though this is mitigated in controlled environments.
• CO2: Requires high pressure and may not be as efficient in warmer climates.
• Propane: Flammability risk, though it’s considered safe in smaller systems with proper design.

Which refrigerant has the lowest global warming potential?

The lowest GWP refrigerant is CO2 (R-744), with a GWP of just 1. This makes it one of the most environmentally friendly refrigerants currently available, particularly for supermarkets aiming to meet sustainability and regulatory requirements.

HFOs vs. natural refrigerants

HFOs are still the go-to for many supermarket applications, especially in North America, due to their ease of retrofitting into existing systems and better handling characteristics compared to natural refrigerants. However, HFOs are still synthetic compounds, and some are concerned about their long-term environmental impact, especially in the case of degradation products.

Natural refrigerants, on the other hand, are seen as the future for truly sustainable refrigeration. Their ultra-low GWP, zero ozone depletion potential, and abundant availability make them appealing. However, they often require significant changes to infrastructure and systems, making the transition more challenging, particularly for large-scale supermarket chains.

Most common low GWP refrigerants for supermarkets today: ●     HFOs: R-448A, R-449A, R-513A ●     Natural Refrigerants: R-744 (CO2), R-290 (propane), NH3 (ammonia) ●     Blends: There are also refrigerant blends being used, like R-410A and R-407A, which are lower-GWP alternatives to traditional HFCs

Summing Up: The Transition to Low GWP Refrigerants

At least for now, HFO refrigerants seem to be a much more practical alternative for most food retailers compared to CO2 and other ultra-low-GWP natural refrigerants, which require a total refrigeration system architecture change — that is, brand new refrigeration compressor systems, piping, refrigerated display cases, and other refrigeration system elements, machinery.

This makes CO2, propane, and ammonia options mostly for new builds and is resulting in resistance to and poor adoption of these refrigerants for existing refrigeration systems. This is the case even during remodels, when the goal for most food retailers is to improve their store sales appearance and offerings as much as possible — not to spend most of their capital replacing their entire existing refrigeration systems, all or much of which may have many years of remaining service life.

But Steve says all eyes are on California at the moment. “According to history, California usually serves as the blueprint for the rest of the country. It’s likely many states will follow what they do.”

The magic GWP number in California and the U.S. appears to be a GWP of less than 150, which delivers a 97 percent reduction in GWP. There are several HFOs that achieve this GWP with very low flammability levels, no toxicity, and the ability to be used as a replacement refrigerant in existing systems as either near drop-in or partial drop-in replacements. Examples include R-455A, R-454C, and R-516A.

For the Near Term: R-448A Refrigerant Retrofits for Food Retail Store Refrigeration Systems

In the meantime, higher-GWP HFO/HFC blends like R-448A are the low GWP refrigerant gas of choice for existing refrigeration systems, requiring only a simple drop-in gas change retrofit, which most of the commercial refrigeration service and contracting industry is able to complete easily.

As of 2020, the HCFC R-22 is no longer produced or imported. Since that time, only recovered, recycled, and reclaimed supplies have been available. As a result, supermarkets are aggressively retrofitting away from R-22 and R404A as their availability is shrinking rapidly. At the moment, most retrofits from the above are to R-448A and R-449A, which are near drop-in retrofits. Steve has overseen such retrofit projects for dozens of supermarkets.

The benefits of a refrigerant retrofit, Steve says, are manifold. “Not only are you switching to a low GWP gas which will be better for the environment, but you’ll also see a return on your investment due to increased energy efficiency.”

He explains, “The replacement HFO refrigerants themselves are more efficient, but also as part of the retrofit process, you’re touching every case and making sure it’s running correctly.” While it’s not technically a total recommissioning, it’s like a recommissioning in that you’re going to perform a lot of corrective tasks along the way. He estimates an improvement in refrigeration system energy efficiency of up to 17 percent for stores transitioning from R-404A to R-448A or R-449A. “And of course, with equipment operating optimally, you’re going to have happier customers.”

At least for now, until we have a clear path forward, Steve recommends an R-448A refrigerant retrofit for all grocery stores that still use HCFCs and HFCs. “At the very least, we know we’re doing less harm to the environment,” Steve says. “And while there may be an initial investment upfront, the cost savings in terms of improved energy efficiency will make it worthwhile.”

“And while there may be an initial investment upfront, the cost savings in terms of improved energy efficiency will make it worthwhile.”

Steve Moss, Head of Refrigeration

The Future of Low GWP Refrigerants

While we can’t tell you exactly what the future holds for refrigerants, manufacturers are working every day to produce new refrigerant gases with the lowest possible GWP ratings. This fact coupled with new legislation coming out all the time can make it hard for FM leaders to keep up. This makes it critical to partner with a provider that’s on the leading edge of sustainable FM solutions.

At City, we offer a comprehensive approach to sustainability, which has been proven to reduce retail clients’ GHG emissions dramatically as well as reducing energy consumption by as much as 25 percent. Our 360-degree carbon management approach is aligned with the Net Zero framework developed by the Science-Based Targets Initiative (SBTi) to prevent refrigerant leaks and reduce energy. Learn more about our sustainability services.