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Plug-in hybrid electric vehicles produce almost 5x more planet-heating pollution than lab-reported data show, according to a new report.

Widening Discrepancy Between Official and Actual CO2 Output

Statistics reveals that PHEVs emit just one-fifth lower CO₂ than traditional petrol and diesel vehicles, based on analysis carried out by a advocacy organization. That contrasts sharply with lab tests, which suggested a three-quarters decrease in emissions.

Researchers studied information from onboard energy use meters of eight hundred thousand vehicles registered in Europe between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, up from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported emissions are falling,” stated a lead researcher participating in the report. “That discrepancy is growing and poses a serious issue. As a result, PHEVs pollute nearly as much as petrol vehicles.”

Key Reasons Driving the Emissions Gap

Analysts attributed most of the gap to overestimates of the “utility factor” – the percentage of kilometers travelled in electric power relative to total distance. The team found that only a quarter of travel was completed in electric mode, whereas lab assumptions assumed 84%.

Even, when operating in electric mode, pollution levels were significantly higher than lab estimates. That happened because electric motors were insufficiently powerful enough to operate independently, resulting to combustion motors using gasoline for almost a third of the distance completed in EV mode.

Regulatory and Financial Consequences

Based on calculations, the underestimation of PHEV CO2 output allowed four major carmaker companies to avoid more than €5bn in penalties between 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would pay about €500 extra annually in operating costs than is assumed under laboratory conditions.

“The bold claims that automakers like to make about their plug-in hybrid vehicles are obviously way off the mark,” commented a transport expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the environment and cutting money. Actually, PHEVs are only slightly better than regular gas and diesel vehicles in terms of fuel use, CO₂ production, and running expenses.”

Political Debate and Industry Lobbying

Hybrid vehicles have lately been brought back into political debates as automakers have pressed the EU to relax CO₂ targets. A proposed prohibition on new combustion engine vehicles in 2035 has faced heavy lobbying from the car sector and resistance from member states with large automotive manufacturing.

Some senior officials have suggested PHEVs as a potential “flexibility” option to include in the legislation.

One independent energy economics expert, who was unaffiliated with the study, called the analysis a “highly valuable contribution” after years in which segments of the car sector argued there was too little information to properly evaluate actual CO2 output.

“The results show, beyond any doubt, that the difference between lab and real-world PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or diesel cars,” the expert said. “Any policy adjustments regarding PHEVs should be implemented with extreme care and considering this data.”