Polestar says it is currently impossible for a consumer to compare the climate impact of different cars.

“The industry has a transparency problem,” said Polestar Head of Sustainability Fredrika Klaren.

Polestar discovered the issue when it was developing its methodology to determine the carbon footprint of its first full-electric car, the Polestar 2 sedan, which the Volvo Cars subsidiary estimates leaves the factory with a carbon footprint of 26 metric tons.

“It became so clear to us that consumers can’t do anything with this number because they can’t compare it,” she told Automotive News Europe during a video chat. “Automakers aren’t sharing their methodologies. And if they are they certainly aren’t sharing them with customers.”

Polestar did get one automaker to share information: its parent company. That is how the 3-year-old brand determined that the Polestar 2’s carbon footprint was 10 metric tons more than the gasoline-powered version of its platform mate, the Volvo XC40, at the end of production.

The biggest contributors to the difference are the Polestar 2’s battery module and its usage of aluminum, which each contributed 29 percent toward the sedan’s carbon footprint from materials production. That amounts to 15 of the Polestar 2’s 26 metric tons of CO2 during production.

After the EV reaches the customer, however, it’s carbon footprint diminishes to 1 metric ton (27 metric tons in total) over an estimated life cycle of 200,000 km — as long as it is recharged solely with renewable energy sources such as wind power.

If coal or other CO2-producing methods of generating electricity are used, the Polestar 2’s life cycle carbon footprint ranged from 50 metric tons to 42 metric tons. The XC40’s life cycle carbon footprint is 58 metric tons, according to Polestar’s calculations.