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Plug-in hybrid electric vehicles emit nearly 5x greater global warming emissions than lab-reported data indicate, according to a recent analysis.

Widening Gap In Lab and Actual Emissions

Data reveals that PHEVs release only 19% lower CO₂ than traditional petrol and diesel cars, according to research carried out by a non-profit organization. This contrasts significantly with lab tests, which assumed a three-quarters decrease in pollution.

Researchers examined data from in-vehicle fuel consumption monitors of eight hundred thousand cars registered in Europe from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, up from three and a half times in 2021.

“Actual emissions are increasing, while official emissions are decreasing,” stated a lead researcher involved in the report. “That discrepancy is growing and poses a significant issue. As a result, PHEVs emit almost as much as gasoline cars.”

Primary Reasons Driving the Discrepancy

Researchers attributed the majority of the difference to inflated estimates of the “utility factor” – the ratio of miles driven in electric mode relative to total mileage. They determined that just a quarter of travel was done in EV mode, while official estimates suggested over four-fifths.

Additionally, when operating in electric mode, pollution amounts were significantly higher than official estimates. This occurred because electric motors were insufficiently powerful sufficient to operate alone, leading to engines using gasoline for almost one-third of the distance completed in EV mode.

Regulatory and Economic Implications

According to estimates, the underestimation of PHEV emissions allowed four major carmaker groups to escape more than €5bn in penalties between 2021 and 2023, by artificially easing compliance with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs would pay about €500 extra per year in running costs than is estimated under lab tests.

“The strong statements that automakers often promote about their plug-in hybrid vehicles are obviously way off the mark,” commented a transport expert. “Consumers are being duped into believing that by buying a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are little improved than regular gas and diesel cars in terms of energy use, CO₂ production, and running costs.”

Policy Discussion and Automotive Pressure

Plug-in hybrid vehicles have recently been drawn back into political discussions as automakers have lobbied the EU to weaken CO₂ targets. A planned prohibition on new internal combustion cars in 2035 has faced heavy pressure from the automotive industry and resistance from EU countries with large car manufacturing.

Several senior officials have suggested PHEVs as a possible “flexibility” option to include in the regulation.

An external energy economics specialist, who was not involved with the study, called the report a “highly valuable addition” after a long period in which segments of the car sector argued there was too little information to properly assess real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the gap in lab and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for petrol or conventional cars,” they stated. “All policy adjustments regarding PHEVs should be made with extreme care and in the light of that data.”