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Plug-in hybrid electric vehicles release almost 5x more planet-heating emissions than lab-reported data indicate, according to a new report.

Growing Discrepancy Between Official and Actual CO2 Output

Data reveals that PHEVs emit only 19% less CO₂ than traditional petrol and diesel cars, based on research conducted by a non-profit group. This contrasts sharply with laboratory tests, which suggested a three-quarters decrease in emissions.

Analysts examined data from onboard energy use meters of eight hundred thousand vehicles sold in the EU between 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than official estimates, up from 3.5 times in 2021.

“Actual emissions are increasing, while official emissions are decreasing,” stated a lead researcher participating in the study. “This gap is growing and poses a serious issue. Consequently, PHEVs emit almost as heavily as gasoline vehicles.”

Key Factors Driving the Discrepancy

Researchers linked the majority of the difference to inflated estimates of the “electric driving share” – the ratio of miles travelled in battery mode compared to overall distance. They found that only 27% of travel was done in EV mode, whereas lab estimates suggested over four-fifths.

Additionally, when running in EV mode, emission amounts were significantly higher than lab projections. That occurred because electric motors were insufficiently powerful sufficient to operate independently, resulting to engines burning fossil fuels for nearly one-third of the travel covered in EV mode.

Policy and Economic Consequences

Based on calculations, the lowballing of PHEV emissions enabled four major carmaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs could pay approximately €500 more annually in operating expenses than is estimated under lab conditions.

“The bold claims that manufacturers often promote about their plug-in hybrid cars are obviously way off the truth,” stated a automotive analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are little better than regular gas and diesel cars in terms of fuel use, CO₂ production, and operating expenses.”

Political Discussion and Industry Lobbying

Plug-in hybrid cars have lately been brought back into political debates as automakers have pressed the European Union to relax CO₂ targets. A planned ban on new internal combustion vehicles in 2035 has faced heavy lobbying from the car industry and opposition from member states with large automotive manufacturing.

Some senior officials have suggested plug-in hybrids as a possible “compromise” solution to introduce in the legislation.

An independent energy policy specialist, who was not involved with the study, called the report a “very useful addition” after a long period in which parts of the automotive sector argued there was insufficient information to properly evaluate actual CO2 output.

“The results show, beyond any doubt, that the gap in lab and actual PHEV energy use and CO₂ emissions is significantly larger than for gasoline or diesel cars,” they stated. “All regulatory changes concerning PHEVs should be made with utmost care and considering this evidence.”