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PHEVs produce nearly 5x more planet-heating pollution than lab-reported figures indicate, according to a new report.

Growing Discrepancy In Lab and Real-World CO2 Output

Data shows that PHEVs emit only one-fifth lower CO₂ than conventional petrol and diesel cars, based on research carried out by a non-profit organization. This differs significantly with lab estimates, which assumed a three-quarters decrease in pollution.

Researchers studied information from in-vehicle fuel consumption meters of eight hundred thousand vehicles sold in Europe between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab figures, increased from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are falling,” stated a lead analyst participating in the study. “This discrepancy is growing and poses a significant problem. As a result, PHEVs pollute nearly as much as gasoline vehicles.”

Primary Factors Driving the Emissions Gap

Researchers attributed most of the gap to overestimates of the “electric driving share” – the ratio of kilometers driven in electric power compared to total mileage. They determined that only a quarter of travel was completed in electric mode, while lab estimates suggested over four-fifths.

Additionally, when running in electric mode, pollution amounts were well above official estimates. This occurred because EV motors were insufficiently powerful enough to operate alone, resulting to combustion motors using fossil fuels for almost one-third of the distance covered in EV mode.

Regulatory and Economic Consequences

Based on estimates, the lowballing of PHEV emissions allowed several large carmaker companies to escape more than €5bn in penalties between 2021 and 2023, by artificially easing adherence with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs would pay approximately €500 more annually in operating costs than would be assumed under lab conditions.

“The strong statements that manufacturers like to make about their plug-in hybrid vehicles are obviously far from the truth,” commented a transport expert. “Consumers are being misled into thinking that by buying a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are little improved than regular petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating costs.”

Policy Debate and Automotive Lobbying

Plug-in hybrid vehicles have lately been drawn back into policy discussions as carmakers have lobbied the European Union to relax CO₂ targets. A proposed prohibition on sales of new internal combustion cars in 2035 has faced intense lobbying from the automotive industry and opposition from EU countries with significant car industries.

Several high-level politicians have proposed plug-in hybrids as a potential “compromise” option to introduce in the regulation.

An independent energy economics specialist, who was unaffiliated with the research, described the report a “very useful addition” after a long period in which segments of the car sector claimed there was insufficient data to accurately evaluate actual emissions.

“These findings show, beyond any doubt, that the gap between lab and actual PHEV energy use and CO₂ output is much, much greater than for gasoline or conventional vehicles,” they said. “Any policy changes concerning PHEVs should be made with utmost care and considering this evidence.”