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Plug-in hybrid electric vehicles produce nearly 5x greater global warming pollution than lab-reported figures show, according to a recent analysis.

Widening Gap In Lab and Real-World Emissions

Statistics reveals that PHEVs release only 19% less CO₂ than traditional petrol and diesel cars, based on analysis conducted by a advocacy organization. That differs sharply with laboratory tests, which assumed a 75% reduction in emissions.

Researchers examined information from in-vehicle fuel consumption meters of 800,000 vehicles registered in Europe from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, increased from three and a half times in 2021.

“Actual CO2 output are increasing, while official emissions are decreasing,” stated a lead analyst involved in the report. “This discrepancy is growing and creates a serious issue. As a result, PHEVs emit nearly as much as petrol vehicles.”

Primary Reasons Behind the Discrepancy

Analysts attributed most of the gap to inflated estimates of the “utility factor” – the ratio of miles travelled in electric power relative to total distance. The team found that just a quarter of travel was completed in electric mode, while lab assumptions suggested 84%.

Even, when running in EV mode, pollution amounts were well above lab estimates. This occurred because EV motors were not strong enough to function independently, leading to engines using gasoline for nearly a third of the distance completed in electric mode.

Policy and Financial Implications

According to calculations, the lowballing of PHEV emissions enabled four large carmaker groups to avoid over €5bn in penalties from 2021 and 2023, by artificially easing adherence with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs could pay about €500 extra annually in operating expenses than would be estimated under laboratory conditions.

“The strong claims that automakers like to make about their plug-in hybrid vehicles are obviously way off the mark,” stated a transport expert. “Consumers are being duped into thinking that by buying a PHEV, they are helping the planet and saving costs. In reality, PHEVs are little better than standard petrol and diesel vehicles in terms of fuel use, CO₂ production, and running costs.”

Political Debate and Automotive Pressure

Hybrid vehicles have recently been brought back into political discussions as carmakers have lobbied the EU to weaken CO₂ targets. A proposed ban on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the car sector and resistance from member states with significant automotive manufacturing.

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

One external energy economics expert, who was unaffiliated with the research, described the analysis a “very useful addition” after a long period in which parts of the automotive sector argued there was too little data to accurately evaluate actual emissions.

“These findings show, beyond any doubt, that the difference between official and real-world PHEV fuel consumption and CO₂ output is significantly larger than for petrol or conventional cars,” the expert said. “All policy adjustments regarding PHEVs should be implemented with utmost care and considering that data.”