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PHEVs produce almost five times more global warming emissions than official figures show, according to a recent analysis.

Widening Gap Between Official and Actual Emissions

Data reveals that PHEVs emit only one-fifth less CO₂ than traditional gas and diesel cars, according to research carried out by a non-profit organization. That contrasts sharply with lab tests, which assumed a three-quarters decrease in emissions.

Analysts examined data from onboard energy use monitors of eight hundred thousand cars registered in Europe between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, up from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are decreasing,” said a lead analyst participating in the report. “That discrepancy is widening and poses a significant problem. Consequently, PHEVs pollute nearly as much as petrol vehicles.”

Key Reasons Driving the Discrepancy

Analysts attributed the majority of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers driven in electric power relative to overall mileage. They found that only a quarter of travel was completed in EV mode, whereas official assumptions assumed 84%.

Even, when running in electric mode, pollution levels were well above official estimates. That happened because electric motors were insufficiently powerful enough to operate independently, leading to engines burning fossil fuels for almost a third of the distance completed in electric mode.

Regulatory and Economic Consequences

Based on calculations, the underestimation of PHEV emissions enabled four large automaker companies to escape over €5bn in fines from 2021 and 2023, by artificially easing adherence with European Union fleet-average CO₂ standards.

Furthermore, owners of PHEVs would spend about €500 more annually in running expenses than would be estimated under lab tests.

“The strong claims that automakers like to make about their plug-in hybrid vehicles are clearly way off the mark,” commented a transport expert. “Buyers are being duped into believing that by buying a PHEV, they are helping the planet and saving costs. In reality, PHEVs are little improved than regular gas and diesel cars in terms of fuel use, CO₂ production, and running expenses.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid cars have recently been drawn back into policy debates as carmakers have lobbied the European Union to relax CO₂ standards. A planned ban on sales of new combustion engine cars in 2035 has faced intense lobbying from the automotive sector and opposition from EU countries with significant automotive manufacturing.

Some senior politicians have suggested plug-in hybrids as a potential “compromise” solution to introduce in the legislation.

An external energy policy expert, who was not involved with the research, described the analysis a “highly valuable contribution” after a long period in which parts of the automotive industry claimed there was insufficient data to accurately evaluate real-world CO2 output.

“These findings demonstrate, without question, that the gap in lab and real-world PHEV fuel consumption and CO₂ emissions is significantly larger than for petrol or conventional cars,” they said. “Any regulatory adjustments regarding PHEVs should be made with extreme care and in the light of this evidence.”