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Plug-in hybrid cars release nearly 5x more planet-heating pollution than lab-reported data show, as per a recent report.

Widening Discrepancy Between Official and Real-World CO2 Output

Data shows that PHEVs release only 19% lower CO₂ than conventional gas and diesel vehicles, based on research carried out by a advocacy group. This differs sharply with laboratory tests, which assumed a 75% reduction in emissions.

Researchers examined information from onboard fuel consumption monitors of eight hundred thousand cars registered in Europe between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than official estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are decreasing,” stated a lead researcher involved in the report. “That discrepancy is widening and creates a significant problem. Consequently, PHEVs emit nearly as much as gasoline vehicles.”

Primary Reasons Driving the Discrepancy

Analysts attributed most of the difference to inflated estimates of the “utility factor” – the ratio of kilometers driven in battery mode compared to total mileage. They found that only a quarter of travel was done in EV mode, while lab assumptions assumed 84%.

Even, when operating in EV mode, emission amounts were well above lab projections. This occurred because EV motors were insufficiently powerful enough to operate alone, leading to engines burning gasoline for almost one-third of the distance covered in electric mode.

Policy and Financial Implications

Based on estimates, the lowballing of PHEV CO2 output allowed several major automaker companies to escape over €5bn in penalties from 2021 and 2023, by falsely easing compliance with European Union fleet-average CO₂ targets.

Additionally, owners of PHEVs could spend approximately €500 extra annually in operating expenses than would be estimated under laboratory tests.

“The strong statements that automakers often promote about their plug-in hybrid vehicles are obviously far from the truth,” commented a transport expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the environment and cutting costs. In reality, PHEVs are little improved than regular gas and diesel cars in terms of energy consumption, CO₂ production, and operating costs.”

Policy Discussion and Industry Pressure

Plug-in hybrid cars have recently been drawn again into political discussions as automakers have lobbied the European Union to weaken CO₂ standards. A planned prohibition on sales of new internal combustion cars in 2035 has faced heavy lobbying from the car sector and resistance from EU countries with significant automotive industries.

Several senior officials have proposed PHEVs as a potential “flexibility” option to include in the regulation.

An independent energy policy expert, who was unaffiliated with the study, called the report a “very useful addition” after years in which segments of the automotive industry argued there was too little information to properly assess actual CO2 output.

“The results show, without question, that the gap between official and real-world PHEV fuel consumption and CO₂ emissions is significantly greater than for petrol or conventional vehicles,” they said. “Any policy changes concerning PHEVs should be made with utmost care and in the light of this evidence.”