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Plug-in hybrid cars release nearly 5x greater global warming pollution than official data show, as per a new report.

Growing Gap Between Lab and Real-World CO2 Output

Statistics shows that PHEVs release just 19% lower CO₂ than traditional gas and diesel cars, based on analysis carried out by a advocacy group. This differs sharply with laboratory estimates, which assumed a three-quarters reduction in emissions.

Researchers examined data from onboard energy use meters of eight hundred thousand vehicles sold in the EU between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, increased from 3.5 times in 2021.

“Actual emissions are rising, while official figures are decreasing,” said a senior analyst involved in the study. “This discrepancy is growing and poses a serious issue. Consequently, PHEVs pollute nearly as much as petrol vehicles.”

Primary Reasons Driving the Emissions Gap

Researchers attributed the majority of the difference to inflated estimates of the “electric driving share” – the ratio of miles travelled in battery power relative to overall distance. They determined that only a quarter of travel was completed in electric mode, while official assumptions assumed 84%.

Even, when running in electric mode, emission levels were significantly higher than lab projections. This occurred because electric motors were not strong enough to operate alone, leading to combustion motors using gasoline for nearly one-third of the travel completed in EV mode.

Regulatory and Financial Implications

According to calculations, the lowballing of PHEV emissions enabled several large automaker groups to escape over €5bn in fines between 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ standards.

Additionally, owners of PHEVs could pay about €500 more per year in running costs than would be assumed under laboratory conditions.

“The strong statements that manufacturers often promote about their plug-in hybrid cars are clearly far from the truth,” stated a automotive expert. “Consumers are being misled into thinking that by buying a PHEV, they are helping the environment and cutting money. In reality, PHEVs are little better than standard petrol and diesel cars in terms of energy consumption, CO₂ emissions, and running expenses.”

Policy Debate and Industry Lobbying

Plug-in hybrid cars have recently been brought back into policy discussions as carmakers have pressed the EU to relax CO₂ targets. A proposed prohibition on sales of new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive industry and resistance from member states with significant car industries.

Some high-level officials have proposed PHEVs as a potential “flexibility” option to introduce in the legislation.

One external energy economics expert, who was unaffiliated with the study, described the report a “highly valuable addition” after years in which parts of the car industry claimed there was insufficient information to properly evaluate actual CO2 output.

“The results demonstrate, beyond any doubt, that the gap between lab and real-world PHEV fuel consumption and CO₂ output is much, much greater than for gasoline or conventional vehicles,” the expert said. “Any regulatory changes regarding PHEVs should be made with utmost caution and in the light of that evidence.”