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Plug-in hybrid electric vehicles release almost 5x greater planet-heating emissions than lab-reported figures indicate, according to a new analysis.

Growing Gap In Lab and Actual Emissions

Data reveals that PHEVs release just 19% less CO₂ than conventional petrol and diesel cars, according to research carried out by a non-profit organization. This contrasts sharply with laboratory tests, which assumed a 75% decrease in emissions.

Researchers examined data from onboard energy use meters of 800,000 vehicles registered in Europe between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab estimates, up from three and a half times in 2021.

“Real-world CO2 output are rising, while official emissions are decreasing,” stated a senior researcher involved in the report. “That discrepancy is widening and poses a significant issue. As a result, PHEVs emit almost as much as gasoline cars.”

Primary Factors Driving the Emissions Gap

Analysts linked most of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in battery power compared to total mileage. They determined that only 27% of travel was completed in electric mode, whereas lab estimates assumed 84%.

Even, when running in electric mode, emission levels were well above lab projections. That happened because EV motors were not strong sufficient to function alone, leading to combustion motors using gasoline for almost a third of the distance completed in EV mode.

Policy and Financial Implications

According to calculations, the lowballing of PHEV emissions enabled several large carmaker companies to escape more than €5bn in fines between 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ targets.

Additionally, owners of PHEVs could pay approximately €500 extra annually in operating costs than is estimated under laboratory conditions.

“The strong statements that automakers like to make about their plug-in hybrid vehicles are obviously far from the truth,” stated a automotive expert. “Buyers are being duped into believing that by purchasing a PHEV, they are helping the environment and saving money. Actually, PHEVs are little better than standard petrol and diesel cars in terms of energy consumption, CO₂ production, and running expenses.”

Political Debate and Automotive Lobbying

Plug-in hybrid cars have recently been drawn again into policy debates as automakers have lobbied the European Union to relax CO₂ targets. A planned prohibition on new internal combustion vehicles in 2035 has faced heavy lobbying from the car sector and resistance from member states with large automotive manufacturing.

Several senior politicians have proposed PHEVs as a potential “compromise” option to introduce in the legislation.

An independent energy policy specialist, who was not involved with the research, described the report a “very useful addition” after years in which parts of the car sector argued there was insufficient information to accurately assess actual emissions.

“These findings demonstrate, without question, that the difference in lab and real-world PHEV energy use and CO₂ emissions is significantly greater than for gasoline or diesel vehicles,” the expert stated. “All policy changes regarding PHEVs should be implemented with extreme care and in the light of this evidence.”