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PHEVs release nearly 5x more planet-heating pollution than lab-reported data indicate, according to a new analysis.

Growing Discrepancy Between Official and Actual CO2 Output

Data shows that PHEVs release just one-fifth less CO₂ than traditional petrol and diesel vehicles, according to research conducted by a advocacy group. This contrasts sharply with lab tests, which suggested a 75% decrease in emissions.

Researchers examined information from in-vehicle fuel consumption meters of 800,000 vehicles sold in Europe between 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, up from 3.5 times in 2021.

“Real-world CO2 output are rising, while official emissions are falling,” stated a lead researcher participating in the study. “This gap is growing and creates a serious problem. As a result, PHEVs pollute nearly as heavily as petrol cars.”

Key Factors Behind the Emissions Gap

Researchers attributed most of the gap to inflated estimates of the “electric driving share” – the percentage of miles travelled in battery power compared to total distance. They determined that only a quarter of driving was done in electric mode, while official estimates assumed 84%.

Additionally, when operating in EV mode, emission amounts were significantly higher than lab estimates. That occurred because electric motors were not strong sufficient to operate independently, leading to engines burning fossil fuels for almost one-third of the travel completed in EV mode.

Policy and Economic Implications

Based on estimates, the underestimation of PHEV emissions allowed four major automaker groups to avoid more than €5bn in fines from 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could pay about €500 more per year in operating costs than is assumed under lab conditions.

“The bold claims that automakers like to make about their PHEV vehicles are obviously far from the mark,” stated a transport analyst. “Consumers are being misled into believing that by buying a PHEV, they are helping the environment and cutting costs. In reality, PHEVs are only slightly better than regular petrol and diesel cars in terms of energy consumption, CO₂ production, and running costs.”

Political Debate and Industry Lobbying

Hybrid cars have recently been drawn back into policy debates as automakers have pressed the European Union to relax CO₂ standards. A proposed ban on new combustion engine vehicles in 2035 has faced intense lobbying from the car industry and resistance from EU countries with large automotive industries.

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

An independent energy economics specialist, who was unaffiliated with the research, described the analysis a “very useful addition” after a long period in which parts of the car industry argued there was too little data to accurately assess real-world emissions.

“These findings show, beyond any doubt, that the gap in official and real-world PHEV energy use and CO₂ emissions is much, much larger than for petrol or diesel vehicles,” the expert said. “All policy adjustments regarding PHEVs should be made with utmost caution and in the light of this evidence.”