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PHEVs emit nearly 5x more planet-heating pollution than lab-reported data indicate, according to a recent report.

Growing Discrepancy Between Lab and Actual Emissions

Data shows that PHEVs emit only one-fifth less CO₂ than conventional gas and diesel cars, according to analysis carried out by a advocacy group. That differs sharply with laboratory tests, which assumed a three-quarters reduction in emissions.

Researchers examined information from onboard energy use meters of 800,000 cars sold in Europe between 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, increased from three and a half times in 2021.

“Actual CO2 output are rising, while official emissions are decreasing,” said a lead analyst involved in the report. “That discrepancy is growing and poses a significant problem. As a result, PHEVs emit nearly as heavily as gasoline cars.”

Primary Factors Driving the Emissions Gap

Analysts attributed most of the gap to inflated estimates of the “utility factor” – the percentage of kilometers travelled in battery power relative to overall mileage. They determined that just a quarter of travel was completed in electric mode, whereas lab assumptions suggested 84%.

Additionally, when operating in electric mode, pollution levels were well above official estimates. That occurred because EV motors were insufficiently powerful sufficient to function independently, leading to combustion motors burning fossil fuels for almost one-third of the travel completed in electric mode.

Regulatory and Economic Consequences

According to estimates, the underestimation of PHEV CO2 output allowed several large automaker companies to avoid over €5bn in fines from 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ targets.

Additionally, owners of PHEVs would pay approximately €500 extra annually in operating expenses than would be assumed under laboratory conditions.

“The bold claims that automakers like to make about their plug-in hybrid cars are clearly far from the mark,” stated a transport analyst. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are little better than standard petrol and diesel cars in terms of fuel use, CO₂ production, and operating expenses.”

Political Debate and Automotive Lobbying

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

Several high-level officials have suggested PHEVs as a possible “flexibility” solution to include in the regulation.

An external energy policy expert, who was not involved with the research, described the report a “highly valuable addition” after a long period in which segments of the car industry argued there was insufficient data to properly evaluate real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the gap between official and real-world PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or conventional vehicles,” the expert said. “All policy adjustments regarding PHEVs should be made with extreme caution and in the light of that evidence.”