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Plug-in hybrid electric vehicles emit nearly five times more global warming emissions than official figures show, according to a recent report.

Widening Gap In Lab and Actual Emissions

Statistics shows that PHEVs release just one-fifth less CO₂ than conventional petrol and diesel vehicles, based on research conducted by a non-profit organization. That differs significantly with lab estimates, which assumed a 75% decrease in pollution.

Researchers studied information from in-vehicle energy use monitors of 800,000 vehicles sold in Europe from 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab figures, up from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are decreasing,” stated a lead researcher involved in the report. “This discrepancy is widening and creates a serious problem. Consequently, PHEVs emit almost as heavily as petrol cars.”

Primary Factors Driving the Discrepancy

Analysts attributed most of the gap to inflated estimates of the “electric driving share” – the ratio of miles driven in battery mode relative to total distance. They determined that just 27% of travel was completed in electric mode, while lab assumptions assumed over four-fifths.

Even, when operating in electric mode, pollution levels were significantly higher than lab estimates. That occurred because EV motors were not strong sufficient to operate independently, resulting to engines using gasoline for almost one-third of the travel completed in EV mode.

Policy and Economic Implications

Based on estimates, the lowballing of PHEV emissions allowed four large carmaker companies to avoid more than €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs could pay about €500 more per year in operating expenses than is assumed under laboratory tests.

“The strong claims that manufacturers like to make about their plug-in hybrid vehicles are clearly way off the truth,” stated a automotive expert. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are little improved than standard petrol and diesel vehicles in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Policy Discussion and Automotive Lobbying

Hybrid vehicles have recently been drawn again into political discussions as carmakers have lobbied the European Union to weaken CO₂ targets. A proposed prohibition on new internal combustion cars in 2035 has faced intense lobbying from the car industry and resistance from EU countries with large automotive manufacturing.

Several high-level politicians have proposed plug-in hybrids as a possible “compromise” solution to introduce in the legislation.

One independent energy policy specialist, who was not involved with the study, described the analysis a “highly valuable addition” after a long period in which segments of the automotive industry argued there was insufficient information to accurately evaluate actual emissions.

“The results show, without question, that the difference between lab and real-world PHEV energy use and CO₂ emissions is much, much greater than for petrol or conventional cars,” the expert said. “Any regulatory changes concerning PHEVs should be implemented with extreme care and in the light of this evidence.”