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Plug-in hybrid electric vehicles produce almost 5x greater global warming pollution than official data show, as per a new report.

Widening Discrepancy Between Official and Actual Emissions

Data shows that PHEVs release just one-fifth lower CO₂ than conventional petrol and diesel cars, according to research carried out by a non-profit group. This differs sharply with lab tests, which assumed a three-quarters decrease in emissions.

Researchers studied data from onboard fuel consumption meters of 800,000 vehicles registered in Europe between 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, up from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are falling,” stated a lead researcher involved in the report. “That gap is growing and poses a serious issue. As a result, PHEVs pollute almost as much as petrol cars.”

Primary Reasons Driving the Discrepancy

Analysts attributed the majority of the gap to inflated estimates of the “utility factor” – the percentage of kilometers travelled in electric power relative to total mileage. They determined that just 27% of travel was completed in EV mode, while lab assumptions assumed 84%.

Even, when operating in EV mode, emission levels were significantly higher than official estimates. That happened because EV motors were not strong enough to operate independently, resulting to engines using gasoline for almost one-third of the distance completed in EV mode.

Policy and Economic Consequences

Based on estimates, the underestimation of PHEV emissions allowed four large carmaker groups to avoid over €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would spend approximately €500 extra annually in running expenses than is assumed under lab tests.

“The strong claims that automakers often promote about their plug-in hybrid vehicles are clearly way off the mark,” commented a automotive expert. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are only slightly better than standard gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and operating costs.”

Policy Discussion and Industry Lobbying

Plug-in hybrid vehicles have lately been brought again into policy discussions as automakers have lobbied the European Union to relax CO₂ targets. A planned ban on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the car industry and opposition from EU countries with significant automotive industries.

Some high-level officials have proposed PHEVs as a possible “flexibility” option to introduce in the regulation.

One external energy economics specialist, who was unaffiliated with the research, called the report a “highly valuable addition” after years in which segments of the car sector claimed there was too little data to properly assess actual CO2 output.

“The results show, beyond any doubt, that the gap in lab and real-world PHEV energy use and CO₂ output is significantly larger than for petrol or conventional cars,” the expert stated. “Any regulatory adjustments concerning PHEVs should be made with extreme caution and in the light of this evidence.”