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Plug-in hybrid electric vehicles emit almost 5x more global warming pollution than official data show, according to a recent analysis.

Growing Discrepancy In Official and Real-World CO2 Output

Statistics reveals that PHEVs release only 19% less CO₂ than conventional petrol and diesel cars, based on research carried out by a advocacy organization. This differs sharply with laboratory tests, which suggested a 75% decrease in emissions.

Analysts examined data from onboard fuel consumption meters of 800,000 cars registered in Europe from 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, up from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported figures are decreasing,” said a senior analyst involved in the study. “That discrepancy is growing and creates a significant issue. Consequently, PHEVs emit almost as much as petrol cars.”

Key Reasons Driving the Discrepancy

Analysts linked the majority of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers driven in electric power relative to overall distance. They determined that just a quarter of travel was completed in electric mode, whereas lab assumptions assumed 84%.

Even, when operating in EV mode, emission levels were significantly higher than lab estimates. That happened because electric motors were insufficiently powerful sufficient to operate alone, leading to combustion motors burning gasoline for almost one-third of the travel completed in electric mode.

Policy and Financial Implications

According to estimates, the underestimation of PHEV emissions enabled four large carmaker groups to avoid over €5bn in fines from 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs would spend approximately €500 more per year in running expenses than would be assumed under laboratory tests.

“The bold statements that manufacturers often promote about their PHEV vehicles are clearly far from the mark,” stated a automotive analyst. “Consumers are being duped into believing that by buying a PHEV, they are helping the planet and saving costs. Actually, PHEVs are little improved than regular gas and diesel cars in terms of fuel use, CO₂ emissions, and operating expenses.”

Policy Debate and Industry Pressure

Hybrid cars have lately been drawn back into policy debates as automakers have lobbied the EU to relax CO₂ targets. A planned prohibition on new combustion engine cars in 2035 has faced intense pressure from the automotive industry and resistance from EU countries with large automotive industries.

Some senior officials have suggested PHEVs as a potential “flexibility” solution to include in the legislation.

One independent energy economics specialist, who was not involved with the study, described the analysis a “very useful addition” after a long period in which segments of the automotive sector claimed there was insufficient data to accurately assess actual CO2 output.

“The results show, beyond any doubt, that the gap in official and real-world PHEV energy use and CO₂ output is significantly greater than for gasoline or conventional cars,” the expert said. “All policy adjustments concerning PHEVs should be made with extreme caution and in the light of this data.”