America’s electric cars are better for the environment, but they share a dirty little secret.

The Chevy Volt, Nissan Leaf and Tesla Roadster all use a super greenhouse gas known as HFC 134a as the refrigerant for their air conditioners. The liquid coolant is so potent that when it leaks into the atmosphere it traps 1,400 times more heat than carbon dioxide over a 100-year time horizon.  

For automakers and advocates of green transportation, it poses an uncomfortable truth: Vehicles touted as a solution to climate change carry a hairspray-sized canister loaded with a chemical that significantly contributes to warming of the earth’s climate. As much as half of current HFC emissions, a small but fast-growing source of global warming pollution, come from leaks out of the air conditioners in cars.

Already a number of Chevrolet, Buick, GMC and Cadillac gas-powered cars use an alternative climate-friendlier coolant called HFO 1234yf, as carmakers confront growing pressure from environmentalists and as regulations are developed by governments. Climate experts say it’s clear that all electric automakers should get on board soon. “It makes sense for electric vehicles to use [alternatives], and to reduce their overall global warming potential,” said Don Anair, deputy director of the clean vehicles program at the Union of Concerned Scientists, a science advocacy group.

But among 16 EV models on America’s roads, only two—Chevy’s newest model of its all-electric Spark and the leaseable Honda Fit—have ditched the super greenhouse gas HFC 134a for the climate safe alternative so far.

Many automakers of both electric cars and conventional ones have expressed reluctance to commit to the switch, citing the cost and limited supply of new alternatives. The European Union has banned HFC 134a for any newly redesigned or reengineered vehicles this year, and for all vehicles in 2017—though the industry elsewhere is not rapidly adopting the EU’s lead. The United States has no such mandate yet. The EPA is considering one.

How countries got to this point is a classic case of unintended environmental consequences. Under the Montreal Protocol, a 1987 treaty that zeroed out substances harmful to the earth’s ozone layer, HFC 134 was chosen by nations as the best alternative at the time to replace ozone-depleting CFCs. The result today is that most of the billion or so cars on the world’s roads use the HFC refrigerant—but while the ozone layer has rebounded, HFC 134a is exacerbating the global warming problem.

So far, HFC 134a and other types of hydrofluorocarbons have contributed to less than one percent of total global warming, according to a study published in the Atmospheric Chemistry and Physics scientific journal. But the use of these damaging gases is climbing generally, as developing world economies use and produce more HFC-spewing cars, air conditioners and refrigerators, and as they make more foam insulation that uses the chemical during manufacture.

Emissions from HFCs are growing at a rate of 10 to 15 percent per year, the study says. Left unchecked, HFCs alone could add up to .5 degree Celsius of the global average temperature rise by the end of the century, about a quarter of the 2 degree Celsius rise that nations are struggling to stay within through international agreements.

EVs and HFC 134a

Electric vehicles are touted for producing zero tailpipe emissions and being a critical force in reducing fossil fuel use and curbing climate-changing pollution—which could make their use of the super greenhouse gas HFC 134a all the more hypocritical.

The Chevy Volt, Nissan Leaf and Tesla Roadster represent about two-thirds of the roughly 180,000 EVs sold in recent years in the United States.

Kevin Kelly, a spokesman for General Motors, wouldn’t say if or when the hybrid Chevy Volt, the biggest selling U.S. EV, might switch to HFO 1234yf.

The auto giant in 2010 said it would be the first U.S. carmaker to voluntarily phase out HFC 134a from many of its passenger cars. So far, only its Chevy Spark EV, which had sold 703 units as of February, and its conventional Cadillac XTS luxury sedan use the new refrigerant. Kelly declined to disclose which other GM models have or will soon follow suit.

Spokespeople for Nissan Motors in the United States were not immediately able to provide more information. Tesla Motors did not respond to repeated requests for comments.

David Doniger, a policy director at the Natural Resources Defense Council who has worked on ozone issues since the 1980s, noted the hypocrisy, but said he is “more concerned about getting the overall transition to occur as quickly as we can.”

All car manufacturers “have the opportunity to switch refrigerants, and they should do it as quickly as they can,” he said. “From an environmental point of view, if you want to get the changeover happening at a large scale, I wouldn’t focus first on electric cars—I’d just be focusing on volume.” Nissan Motors, for instance, sold 1.2 million gas cars in the U.S. in 2013, and just 23,000 all-electric Leafs.

What has made vehicle air conditioners a primary concern of advocates is that the refrigerants often leak into the air slowly over years. Cars that are dumped or crushed in the junkyard usually leak, too, since there’s little regulatory or economic incentive for mechanics to collect and destroy old coolant.

The leading alternative to HFC 134a developed so far is HFO 1234yf, a hydrofluoroolefin compound, sometimes described simply as “YF,” which traps about as much heat in the atmosphere as carbon dioxide does. YF has 0.3 percent the climate impact of HFC 134a. It is available in nearly a dozen car models, and about half a million vehicles worldwide run it through their air conditioning systems, according to Honeywell, the New Jersey-based industrial conglomerate and marketer of YF. Honeywell expects more than two million vehicles to use the refrigerant by the end of this year.

Through a joint venture with Delaware-based DuPont Co., Honeywell operates a manufacturing facility in China. Last December, the company announced plans to build a $300 million YF facility in Geismar, La., that is expected to come online in 2016.

But while YF works well, it needs more energy to do its job—10 percent or more energy by some estimates. In an electric vehicle, cooling and heating already use up a significant part of the battery’s juice, shortening the car’s driving range and making a more energy-intensive refrigerant less attractive, according to Stephen Andersen, who directed ozone protection and climate programs in the EPA for more than two decades.

Andersen also cited concerns about YF’s availability and being able to get it serviced in auto shops. Using the new refrigerant “would be one more albatross for the electric car,” said Anderson, who is now U.S. director of research at the Institute for Governance & Sustainability. Electric vehicle drivers already face a dearth of options for recharging their batteries on the road even at daily commuting distances—a factor in low sales.

The all-electric Chevy Spark EV—which debuted in California and Oregon last year—and the Honda Fit EV, available for lease in the United States, are bucking those concerns, however. Both use YF.

In Europe, a Fight to Keep HFCs

YF has hardly won universal acceptance.

In Europe, Germany’s largest automakers are refusing to use YF, creating a standoff that is slowing down the switch, Bloomberg News reported last year.

The European Union, meanwhile, has prohibited HFC 134a from newly designed cars. By 2017, it will be banned from all new cars there. Yet, parent company Daimler AG said it would recall its new Mercedes-Benz cars that contain YF, after the product failed internal safety tests, and use HFC 134a instead—a violation of the EU’s new regulations. According to the company, in some head-on collision test scenarios, YF burst into flames. Volkswagen AG said it would re-evaluate HFO 1234yf and put off plans to use it “until further notice.”

HFO 1234yf passed industry and U.S. EPA evaluations, and General Motors is standing by the alternative refrigerant despite Daimler’s tests. Earlier this month, EU scientists said they found the chemical does not pose any serious safety risks and the European Commission recently launched a legal proceeding against Daimler for its refusal to get rid of HFC 134a in Mercedes-Benz cars.

German automakers are proposing to use a different alternative instead—a carbon dioxide-based refrigerant called R744 that has a global warming potential similar to HFO 1234yf. Daimler, Volkswagen and Audi, BMW and Porsche said last year that they would steadily roll out their new technology across their respective fleets.

Rise and Fall of HFC 134a, and What’s Ahead

Before HFC 134a became a key climate concern, it was the best-available clean alternative and the one most easily adopted worldwide.

In the late 1970s and 80s, scientists observed that its predecessor, CFC 12, was depleting the Earth’s ozone layer, exposing the planet to more of the sun’s harmful radiation, particularly above the South Pole. In 1987, participants in the Montreal Protocol agreed to start phasing-out chlorofluorocarbons entirely, and by 1995, the United States had banned production and import of CFCs and other ozone depleting substances.

CFC 12 was also a powerful global warming agent, able to trap nearly 11,000 times more heat in the atmosphere than carbon dioxide. HFC 134a is considered ozone safe, and has one-eighth the global warming potential of CFC 12.

“It was considered a victory for both the climate and ozone,” said Anderson, the former EPA director who has also played an instrumental role in implementing the Montreal Protocol.

Doniger, who also participated in the Montreal Protocol negotiations, recalled that the chemical industry had resisted calls for developing brand-new refrigerants. Hydroflurocarbons, far less damaging than CFCs as a greenhouse gas, emerged as a practical choice and won acceptance, Doniger said, “even though we knew that this second generation of refrigerants were not perfect.”

The changes brought by the Montreal Protocol have succeeded, Doniger explained, because the treaty was designed to force practical rules that would evolve gradually. For example, CFCs, the original threat to Earth’s ozone layer are still allowed for use as a propellant in medical inhalers for asthma, though new alternatives promise to end even that exception. HFCs, still a small contributor to climate change, are growing enough to become a new concern. YF is now a viable alternative. “We need to keep going,” Doniger said.

The Montreal Protocol is an ongoing process, with more than a hundred countries meeting twice a year to hash out improvements by proposing how nations must phase out greenhouse gas usage as industry discovers smarter alternatives. For years, reducing and eliminating HFCs, especially in air conditioning, has been debated with Micronesian island nations and North America pushing proposals. China has agreed to cooperate and follow the lead of the United States. India, Doniger said, has emerged as a key opponent, for now.

A major effort by U.S. climate change activists is underway to phase out HFC 134a and other super-potent greenhouse gases in the United States. President Obama’s new slate of aggressive fuel efficiency standards gives automakers incentives to make the switch. Companies that use cleaner refrigerants, such as HFO 1234yf, or install systems that significantly stop leaks can earn credits toward the federal requirements that force automakers to increase fuel efficiency standards.

Last month, the U.S. EPA laid out a schedule for proposing tougher regulations under the federal Clean Air Act to directly require the replacement of HFC 134a and other HFCs with newer, lower-impact alternatives. Doniger said he expects the agency will issue a proposal in the next six months. The rules could “accelerate the industry-wide transition away from HFC 134a,” he said, by forcing automakers to use alternatives on a rapid schedule beginning next year.

If efforts succeed they could substantially eliminate the global warming emissions caused by HFCs and “significantly improve the chances of staying below the 2-degree Celsius global warming guardrail,” according to the study in Atmospheric Chemistry and Physics. That subject will be on the table for Montreal Protocol meetings later this year.

“We could eliminate one of the six [main] greenhouse gases,” said Durwood Zaelke, president of the the Institute for Governance & Sustainability. “The consensus has gotten stronger and stronger that this needs to be done,” Zaelke said.