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

Widening Discrepancy Between Lab and Real-World Emissions

Data reveals that PHEVs release just one-fifth less CO₂ than conventional petrol and diesel cars, according to research carried out by a non-profit organization. This differs significantly with lab tests, which suggested a 75% decrease in pollution.

Analysts studied information from in-vehicle fuel consumption meters of 800,000 vehicles sold in the EU from 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were nearly five times greater than lab figures, up from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported figures are decreasing,” said a lead researcher participating in the study. “That gap is growing and poses a significant problem. As a result, PHEVs emit almost as heavily as gasoline cars.”

Key Reasons Behind the Emissions Gap

Analysts attributed most of the gap to inflated estimates of the “utility factor” – the ratio of miles driven in battery power relative to total distance. They found that only 27% of driving was completed in EV mode, while lab estimates assumed 84%.

Even, when running in EV mode, emission levels were significantly higher than official projections. This happened because electric motors were not strong enough to operate alone, resulting to combustion motors burning gasoline for nearly one-third of the travel completed in EV mode.

Policy and Financial Consequences

According to calculations, the underestimation of PHEV emissions enabled several large automaker companies to avoid more than €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ standards.

Furthermore, owners of PHEVs would pay approximately €500 extra per year in running expenses than would be assumed under laboratory tests.

“The bold claims that automakers like to make about their plug-in hybrid vehicles are clearly way off the truth,” stated a transport expert. “Buyers are being duped into believing that by buying a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are only slightly improved than regular gas and diesel vehicles in terms of energy consumption, CO₂ production, and operating costs.”

Political Discussion and Automotive Lobbying

Plug-in hybrid cars have lately been brought back into policy debates as carmakers have lobbied the European Union to relax CO₂ standards. A planned prohibition on sales of new internal combustion cars in 2035 has faced heavy lobbying from the automotive industry and opposition from EU countries with significant car manufacturing.

Several high-level officials have proposed PHEVs as a possible “compromise” option to include in the regulation.

An independent energy economics specialist, who was unaffiliated with the study, described the analysis a “very useful contribution” after years in which parts of the car industry argued there was too little information to accurately evaluate actual CO2 output.

“The results demonstrate, without question, that the difference in official and actual PHEV fuel consumption and CO₂ output is significantly greater than for petrol or conventional vehicles,” the expert stated. “All policy adjustments concerning PHEVs should be implemented with extreme caution and in the light of this evidence.”