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Plug-in hybrid cars release almost 5x more global warming pollution than official figures show, according to a recent report.

Widening Gap In Lab and Real-World CO2 Output

Data reveals that PHEVs release just one-fifth lower CO₂ than conventional petrol and diesel cars, based on analysis carried out by a non-profit group. That contrasts significantly with laboratory tests, which suggested a 75% decrease in pollution.

Analysts examined data from onboard energy use monitors of 800,000 cars registered in Europe between 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official estimates, increased from three and a half times in 2021.

“Real-world emissions are increasing, while official figures are falling,” said a lead analyst involved in the report. “That gap is widening and creates a significant problem. As a result, PHEVs pollute nearly as heavily as petrol vehicles.”

Primary Reasons Behind the Discrepancy

Analysts linked the majority of the difference to overestimates of the “electric driving share” – the percentage of kilometers driven in electric mode relative to overall distance. They found that just 27% of driving was done in electric mode, while official assumptions suggested 84%.

Additionally, when running in EV mode, emission amounts were well above lab estimates. This occurred because electric motors were insufficiently powerful sufficient to operate independently, leading to engines using fossil fuels for almost a third of the travel covered in EV mode.

Regulatory and Financial Consequences

According to calculations, the lowballing of PHEV CO2 output allowed four major automaker groups to avoid more than €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ standards.

Furthermore, owners of PHEVs could spend about €500 more per year in running costs than would be estimated under laboratory conditions.

“The strong statements that manufacturers often promote about their PHEV vehicles are clearly way off the truth,” stated a transport expert. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are little better than regular gas and diesel cars in terms of energy use, CO₂ emissions, and running expenses.”

Political Debate and Industry Pressure

Plug-in hybrid cars have lately been drawn again into policy debates as carmakers have pressed the European Union to relax CO₂ standards. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced intense lobbying from the automotive sector and resistance from EU countries with large car industries.

Some high-level officials have suggested PHEVs as a possible “flexibility” solution to include in the legislation.

One external energy economics expert, who was not involved with the research, called the analysis a “highly valuable contribution” after a long period in which segments of the automotive industry claimed there was insufficient data to properly assess real-world CO2 output.

“The results show, beyond any doubt, that the gap in official and real-world PHEV fuel consumption and CO₂ output is much, much larger than for petrol or conventional vehicles,” they stated. “Any policy adjustments regarding PHEVs should be implemented with extreme care and in the light of this data.”