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Plug-in hybrid electric vehicles emit nearly 5x more global warming emissions than official data indicate, according to a new report.

Widening Gap In Lab and Actual Emissions

Statistics shows that PHEVs release just 19% lower CO₂ than traditional petrol and diesel cars, according to analysis carried out by a non-profit group. This differs sharply with laboratory tests, which assumed a three-quarters decrease in emissions.

Analysts examined data from in-vehicle energy use monitors of eight hundred thousand cars sold in Europe between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were nearly five times greater than lab figures, up from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are decreasing,” stated a lead analyst involved in the study. “This gap is widening and creates a serious issue. As a result, PHEVs pollute nearly as heavily as petrol cars.”

Primary Reasons Behind the Emissions Gap

Researchers attributed most of the gap to overestimates of the “utility factor” – the ratio of miles travelled in electric mode relative to overall distance. They determined that just 27% of driving was completed in electric mode, while lab assumptions assumed 84%.

Additionally, when operating in electric mode, pollution levels were well above lab estimates. This occurred because electric motors were not strong enough to operate independently, resulting to combustion motors burning gasoline for nearly a third of the travel covered in EV mode.

Regulatory and Financial Consequences

Based on calculations, the lowballing of PHEV emissions allowed several major carmaker companies to avoid over €5bn in fines between 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ standards.

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

“The strong statements that manufacturers often promote about their plug-in hybrid cars are clearly far from the truth,” commented a transport expert. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are little better than standard gas and diesel cars in terms of fuel consumption, CO₂ emissions, and operating costs.”

Policy Debate and Industry Lobbying

Hybrid cars have lately been drawn back into political discussions as carmakers have pressed the European Union to weaken CO₂ targets. A proposed prohibition on sales of new internal combustion cars in 2035 has faced heavy lobbying from the car sector and opposition from member states with large automotive industries.

Several senior politicians have proposed plug-in hybrids as a possible “flexibility” option to introduce in the regulation.

One external energy economics specialist, who was unaffiliated with the research, described the report a “highly valuable contribution” after years in which parts of the automotive industry claimed there was insufficient information to properly assess real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the difference between lab and real-world PHEV energy use and CO₂ output is much, much greater than for petrol or conventional cars,” the expert stated. “Any policy adjustments regarding PHEVs should be implemented with extreme care and considering that data.”