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Plug-in hybrid electric vehicles produce nearly five times greater planet-heating emissions than official data show, as per a new report.

Widening Discrepancy In Official and Actual CO2 Output

Data reveals that PHEVs emit just 19% lower CO₂ than conventional gas and diesel vehicles, according to research conducted by a advocacy organization. This contrasts significantly with laboratory estimates, which assumed a three-quarters reduction in emissions.

Researchers studied information from onboard energy use meters of eight hundred thousand cars sold in Europe between 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official figures, up from three and a half times in 2021.

“Real-world CO2 output are rising, while official emissions are falling,” said a senior researcher participating in the report. “This gap is widening and poses a significant problem. Consequently, PHEVs pollute nearly as much as gasoline cars.”

Key Factors Driving the Discrepancy

Analysts linked most of the gap to overestimates of the “utility factor” – the ratio of miles travelled in battery power relative to total distance. The team determined that just a quarter of driving was completed in EV mode, whereas official estimates suggested 84%.

Even, when operating in EV mode, pollution levels were well above lab estimates. That occurred because EV motors were not strong sufficient to function independently, leading to engines using fossil fuels for nearly one-third of the distance completed in electric mode.

Policy and Economic Implications

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

Additionally, owners of PHEVs would pay approximately €500 more per year in operating expenses than would be assumed under laboratory conditions.

“The strong claims that automakers often promote about their PHEV cars are clearly way off the mark,” commented a transport expert. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are little better than standard petrol and diesel cars in terms of fuel use, CO₂ emissions, and operating expenses.”

Policy Debate and Industry Pressure

Plug-in hybrid cars have recently been brought again into policy discussions as carmakers have pressed the EU to weaken CO₂ targets. A planned ban on new combustion engine vehicles in 2035 has faced heavy lobbying from the car industry and opposition from EU countries with large car industries.

Several high-level officials have proposed PHEVs as a potential “flexibility” solution to introduce in the legislation.

An external energy economics specialist, who was unaffiliated with the study, described the analysis a “very useful contribution” after a long period in which parts of the car industry argued there was too little data to properly assess actual emissions.

“These findings demonstrate, beyond any doubt, that the gap between official and real-world PHEV energy use and CO₂ output is significantly larger than for petrol or diesel vehicles,” the expert said. “All regulatory adjustments concerning PHEVs should be made with utmost caution and in the light of this evidence.”