Plug-in vehicles pollute more than previously thought, study shows

Hybrid cars with external electric charging emit up to five times more carbon dioxide in real-world conditions than the calculations on which European Union regulations are based, according to a study published on Thursday.

The study conducted by the environmental NGO International Council on Clean Transportation (ICCT) shows a ‘significant and growing gap between CO2 emissions in real driving conditions and those measured during homologation tests’ for hybrid cars with external electric charging, known as plug-in cars, registered between 2021 and 2023.

Specifically, average carbon dioxide emissions in real conditions were 3.5 times higher than the values obtained during homologation in 2021 and 4.6 times higher than the calculations in 2023.

The main reason for this discrepancy is that this type of vehicle ‘is charged less frequently and driven in electric mode less often than expected’ in the initial calculations, states ICCT.

This NGO is behind the revelations of the Dieselgate scandal, which has shaken major car manufacturers since 2015, accused of concealing the actual levels of nitrogen oxides (NOx) pollution.

Peter Mock, director of the European branch of ICCT, says that ‘this may seem contradictory, but the increase in electric range of new models has not actually led to greater use of electric driving mode.’

A revision of the calculation methodology expected next year ‘will likely reduce the attractiveness of hybrid cars with external electric charging as a means for manufacturers to meet European CO2 emission targets for new cars,’ warns Peter Mock. ‘It should also lead to a further reduction in their market share.’

According to ICCT, hybrid cars with external electric charging accounted for about 10 percent of registered new cars in Europe from January to July 2026, compared to 9 percent in the same period last year, while fully electric cars reached a market share of 22 percent during the same period.

This study was published at a time when hybrid cars with external electric charging are among the technologies that some car manufacturers, particularly German ones, want to remain included in the European decarbonization strategy for the automotive sector.

At Germany’s urging, the European Commission proposed in December to abandon the ban on the sale of new cars with internal combustion engines from 2035, to offer the industry greater flexibility.

Instead, manufacturers would have to reduce CO2 emissions by 90 percent compared to 2021 levels, and compensate for the remaining 10 percent of emissions.

The German coalition government, according to media reports, wants to enable greater representation of hybrid vehicles.

To avoid a ‘strategic mistake,’ seven countries, including France, called on the European Union in June to maintain an ‘ambitious direction’ in favor of electric vehicles.