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Plug-in hybrid cars produce almost five times more global warming pollution than lab-reported data indicate, as per a recent report.

Widening Gap Between Official and Real-World Emissions

Data shows that PHEVs emit just 19% lower CO₂ than traditional petrol and diesel vehicles, based on analysis conducted by a non-profit group. That differs sharply with lab tests, which suggested a three-quarters reduction in emissions.

Researchers examined information from in-vehicle energy use meters of 800,000 vehicles sold in Europe between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, increased from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported emissions are decreasing,” stated a lead analyst involved in the report. “That discrepancy is widening and creates a serious issue. As a result, PHEVs pollute nearly as heavily as petrol cars.”

Primary Factors Driving the Emissions Gap

Researchers attributed the majority of the difference to overestimates of the “utility factor” – the ratio of miles driven in battery power relative to total mileage. The team determined that only a quarter of travel was done in electric mode, whereas lab assumptions suggested over four-fifths.

Additionally, when running in electric mode, emission amounts were significantly higher than official projections. That happened because EV motors were not strong enough to function independently, resulting to combustion motors burning fossil fuels for nearly one-third of the travel completed in electric mode.

Regulatory and Economic Consequences

According to calculations, the underestimation of PHEV emissions allowed several large carmaker groups to escape more than €5bn in fines between 2021 and 2023, by falsely easing adherence with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would pay about €500 more annually in running expenses than would be estimated under laboratory tests.

“The bold statements that automakers often promote about their plug-in hybrid cars are clearly way off the mark,” commented a transport expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are little better than regular gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and operating costs.”

Policy Discussion and Industry Pressure

Hybrid vehicles have recently been brought back into policy discussions as carmakers have lobbied the European Union to relax CO₂ targets. A proposed ban on new internal combustion vehicles in 2035 has faced intense lobbying from the car sector and resistance from member states with significant car manufacturing.

Some high-level politicians have proposed PHEVs as a potential “flexibility” solution to introduce in the legislation.

An independent energy economics specialist, who was not involved with the study, called the analysis a “very useful addition” after years in which segments of the car sector claimed there was too little information to properly assess actual CO2 output.

“These findings demonstrate, beyond any doubt, that the difference in lab and actual PHEV energy use and CO₂ emissions is significantly larger than for petrol or diesel vehicles,” the expert said. “All policy adjustments concerning PHEVs should be made with utmost care and in the light of that data.”