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PHEVs release almost 5x greater planet-heating pollution than lab-reported data show, as per a new report.

Widening Discrepancy Between Official and Actual CO2 Output

Data shows that PHEVs release just 19% less CO₂ than traditional petrol and diesel cars, according to research carried out by a non-profit organization. That contrasts sharply with laboratory tests, which suggested a three-quarters reduction in pollution.

Researchers examined information from in-vehicle energy use monitors of eight hundred thousand vehicles sold in Europe from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, up from three and a half times in 2021.

“Real-world CO2 output are rising, while official figures are falling,” said a senior researcher participating in the report. “That discrepancy is growing and creates a significant problem. As a result, PHEVs pollute almost as heavily as petrol vehicles.”

Key Reasons Behind the Emissions Gap

Analysts attributed the majority of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in battery power compared to overall distance. They determined that just a quarter of travel was done in EV mode, while official assumptions suggested over four-fifths.

Additionally, when running in electric mode, emission amounts were significantly higher than official estimates. This happened because EV motors were not strong enough to operate independently, leading to combustion motors using gasoline for nearly one-third of the distance completed in electric mode.

Policy and Financial Implications

Based on calculations, the underestimation of PHEV CO2 output allowed four large carmaker groups to escape over €5bn in penalties between 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs could spend about €500 more per year in operating expenses than would be estimated under laboratory conditions.

“The strong statements that manufacturers often promote about their plug-in hybrid cars are obviously way off the mark,” stated a transport expert. “Consumers are being misled into thinking that by buying a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are only slightly better than standard petrol and diesel cars in terms of energy consumption, CO₂ production, and operating expenses.”

Policy Debate and Automotive Lobbying

Plug-in hybrid vehicles have lately been drawn back into policy debates as carmakers have pressed the EU to weaken CO₂ targets. A proposed prohibition on new combustion engine cars in 2035 has faced intense lobbying from the car sector and resistance from EU countries with large car manufacturing.

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

An independent energy policy expert, who was unaffiliated with the research, described the analysis a “very useful contribution” after a long period in which segments of the automotive sector claimed there was too little information to properly evaluate actual CO2 output.

“These findings demonstrate, beyond any doubt, that the difference in lab and real-world PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or diesel vehicles,” the expert stated. “Any regulatory adjustments concerning PHEVs should be made with extreme care and considering that evidence.”