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Plug-in hybrid cars produce nearly 5x greater global warming emissions than lab-reported data show, as per a new analysis.

Growing Discrepancy In Lab and Real-World Emissions

Statistics shows that PHEVs emit just 19% less CO₂ than traditional petrol and diesel cars, according to analysis carried out by a non-profit organization. This contrasts sharply with laboratory estimates, which assumed a three-quarters decrease in emissions.

Researchers examined data from onboard energy use monitors of eight hundred thousand vehicles sold in Europe from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times greater than official figures, increased from 3.5 times in 2021.

“Actual emissions are rising, while official figures are falling,” said a lead analyst involved in the report. “That discrepancy is growing and creates a serious problem. Consequently, PHEVs emit almost as much as gasoline cars.”

Primary Factors Behind the Emissions Gap

Researchers attributed the majority of the difference to overestimates of the “utility factor” – the percentage of kilometers driven in battery mode relative to total distance. They determined that just a quarter of driving was done in electric mode, whereas official assumptions suggested over four-fifths.

Even, when operating in electric mode, pollution levels were significantly higher than lab projections. This occurred because electric motors were not strong sufficient to function alone, leading to combustion motors burning fossil fuels for nearly one-third of the travel covered in electric mode.

Policy and Economic Consequences

According to estimates, the lowballing of PHEV emissions enabled several large automaker groups to avoid over €5bn in penalties from 2021 and 2023, by falsely easing adherence with European Union fleet-average CO₂ standards.

Furthermore, drivers of PHEVs would pay approximately €500 more per year in operating expenses than would be assumed under lab tests.

“The bold statements that automakers like to make about their plug-in hybrid cars are clearly far from the mark,” commented a automotive expert. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are only slightly better than standard gas and diesel cars in terms of energy consumption, CO₂ emissions, and operating costs.”

Policy Debate and Industry Lobbying

Plug-in hybrid cars have recently been brought back into policy debates as automakers have lobbied the European Union to weaken CO₂ targets. A planned prohibition on new internal combustion vehicles in 2035 has faced heavy lobbying from the automotive sector and resistance from EU countries with significant car manufacturing.

Some high-level officials have proposed plug-in hybrids as a possible “flexibility” option to introduce in the legislation.

An external energy policy specialist, who was unaffiliated with the research, described the analysis a “very useful addition” after a long period in which segments of the car industry claimed there was insufficient information to properly evaluate real-world CO2 output.

“These findings show, without question, that the gap in official and real-world PHEV fuel consumption and CO₂ output is much, much larger than for petrol or conventional cars,” they said. “All policy adjustments concerning PHEVs should be made with extreme care and considering that evidence.”