German car manufacturer Volkswagen has modified its established CO2 (R744) heat pump to provide cooling and heating in its new subcompact class of electric vehicles (EVs).
Two Volkswagen executives – Felix Nowak-Walenta, Thermal Management Test Engineer, and Carsten Wachsmuth, Thermal Management of EVs, Research and Development Division – explained the modification and gave an update on the progress of the company’s CO2 heat pump rollout for electric vehicles on September 29 the ATMO MAC Summit 2026 x TU Berlin in Brussels. The speakers also presented at previous ATMO MAC conferences.
ATMO MAC Summit 2026 x TU Berlin was organized by ATMOsphere, publisher of NaturalRefrigerants.com, in partnership with Technische Universität (TU) Berlin’s Department of Heat Transfer and Heat Conversion.
Volkswagen, one of the leaders in the adoption of CO2 heat pumps for electric vehicles, has sold more than 1.5 million CO2 units since 2000, adding five million since 2024. These are mostly in the European market, with a small number in Canada. “Every year, R744 grows faster than the year before, and in the subcompact segment, sales have only just begun,” said Wachsmuth.
Last year, Volkswagen announced plans to unveil subcompact electric vehicles in 2026 using its new MEB+ electric platform, with a starting price of around €25,000 ($28,000). The smaller cars employ a new unified cell in the battery for the first time, enabling driving ranges of up to 450km (280 miles).
Engineering challenge
Adapting heat pump systems from larger models (ID4, ID Bus and ID7) to subcompact vehicles presented an engineering challenge, noted Nowak-Walenta. “The smaller the car gets, the heating and cooling demand goes down, but the package also goes smaller, and that’s where the challenge arises for us to get a scalable system into these cars.” As a result, a smaller heat pump system has been designed to combine functions, including shared heat exchangers, in the MEB+ platform.
The subcompact cars use a smaller HVAC system, which does not integrate an air heater for the passenger cabin “and therefore we have another system to heat up the air,” explained Wachsmuth. The new design employs a separate heater (heat exchanger), with heated glycol going to the cabin as well as to the battery when necessary. “Therefore we put a lot more complexity on the coolant [glycol] side,” he said. Legacy system use a separate glycol heater only for the battery, while heat from the CO2 warms the cabin.
“Every year, R744 grows faster than the year before, and in the subcompact segment, sales have only just begun.”
Carsten Wachsmuth, Volkswagen
By contrast, in the summer, the AC cycle in the smaller cars uses the CO2 to cool the cabin, while chilled glycol cools the battery when necessary, Wachsmuth noted. This design incorporates CO2 check valves for the first time while the complexity of the refrigerant circuit decreases slightly. Overall the A/C operation is comparable to the compact class heat pump design.
Nowak-Walenta noted that short drives, such as commuting to work, dominate car usage, with two-thirds having a duration of less than 20 minutes. But the more an electric vehicle is used for short drives at low speeds, particularly in cold weather, “the more it profits from a heat pump,” he said. “This is where our customers use [their cars], so that’s where we can help them save energy with a heat pump. That’s what we’re doing with our R744 system.”
