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Plug-in hybrid electric vehicles release nearly 5x more global warming pollution than official figures indicate, as per a new report.

Growing Gap Between Lab and Actual Emissions

Data reveals that PHEVs release only one-fifth less CO₂ than traditional gas and diesel vehicles, based on analysis conducted by a non-profit organization. This contrasts significantly with lab tests, which suggested a 75% reduction in emissions.

Researchers studied data from onboard fuel consumption monitors of 800,000 cars registered in the EU from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab estimates, up from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported figures are decreasing,” stated a lead researcher involved in the study. “That discrepancy is widening and poses a serious problem. Consequently, PHEVs emit almost as much as petrol vehicles.”

Primary Reasons Behind the Emissions Gap

Analysts attributed most of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in battery mode relative to overall mileage. The team found that only a quarter of travel was completed in EV mode, whereas lab assumptions suggested over four-fifths.

Additionally, when operating in EV mode, emission levels were significantly higher than official estimates. This happened because electric motors were not strong sufficient to operate alone, leading to engines using gasoline for almost a third of the distance completed in electric mode.

Regulatory and Financial Consequences

According to estimates, the underestimation of PHEV CO2 output enabled several large carmaker companies to avoid more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ targets.

Additionally, owners of PHEVs would pay about €500 extra annually in running expenses than is assumed under lab conditions.

“The strong statements that manufacturers like to make about their PHEV cars are obviously far from the mark,” commented a automotive analyst. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are little improved than regular gas and diesel vehicles in terms of energy consumption, CO₂ production, and operating expenses.”

Political Discussion and Automotive Lobbying

Plug-in hybrid vehicles have recently been drawn back into political discussions as automakers have lobbied the EU to weaken CO₂ standards. A proposed ban on new internal combustion vehicles in 2035 has faced intense pressure from the automotive industry and resistance from EU countries with large car industries.

Several high-level officials have proposed plug-in hybrids as a potential “flexibility” option to include in the regulation.

An independent energy policy expert, who was not involved with the study, described the report a “highly valuable contribution” after years in which segments of the car sector argued there was insufficient data to accurately assess actual emissions.

“These findings demonstrate, without question, that the difference between lab and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or diesel cars,” the expert stated. “All policy adjustments concerning PHEVs should be implemented with utmost care and considering this data.”