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Plug-in hybrid electric vehicles produce almost five times greater global warming pollution than lab-reported data indicate, according to a recent report.

Growing Discrepancy Between Lab and Actual Emissions

Statistics shows that PHEVs release only one-fifth lower CO₂ than conventional gas and diesel vehicles, according to research carried out by a non-profit group. This differs sharply with laboratory estimates, which assumed a 75% reduction in emissions.

Researchers studied information from onboard energy use monitors of 800,000 cars sold in the EU between 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, up from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are falling,” stated a senior researcher involved in the study. “This discrepancy is growing and poses a serious problem. Consequently, PHEVs pollute almost as heavily as gasoline vehicles.”

Primary Factors Driving the Emissions Gap

Researchers linked most of the gap to inflated estimates of the “utility factor” – the ratio of kilometers driven in battery power relative to total distance. The team determined that just a quarter of travel was completed in EV mode, whereas lab estimates assumed 84%.

Additionally, when operating in electric mode, pollution amounts were well above official projections. That happened because electric motors were insufficiently powerful sufficient to function independently, resulting to engines burning fossil fuels for almost a third of the travel covered in electric mode.

Policy and Financial Implications

According to estimates, the lowballing of PHEV CO2 output allowed four major automaker companies to avoid more than €5bn in fines from 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs would spend about €500 extra annually in running costs than is estimated under laboratory tests.

“The bold statements that automakers like to make about their plug-in hybrid vehicles are clearly way off the mark,” commented a automotive expert. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are little improved than regular petrol and diesel cars in terms of fuel consumption, CO₂ production, and running expenses.”

Political Debate and Automotive Lobbying

Plug-in hybrid vehicles have lately been drawn again into policy discussions as carmakers have lobbied the European Union to relax CO₂ targets. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced intense pressure from the car industry and opposition from member states with large automotive manufacturing.

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

An independent energy economics specialist, who was not involved with the study, called the report a “highly valuable contribution” after a long period in which parts of the car industry argued there was insufficient data to accurately evaluate actual emissions.

“These findings demonstrate, beyond any doubt, that the difference in lab and actual PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or diesel vehicles,” they said. “Any regulatory adjustments regarding PHEVs should be made with extreme care and in the light of that evidence.”