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Plug-in hybrid cars produce almost five times greater global warming pollution than official figures indicate, according to a recent analysis.

Widening Gap Between Lab and Actual CO2 Output

Data shows that PHEVs emit just one-fifth less CO₂ than traditional petrol and diesel cars, based on analysis conducted by a advocacy group. This differs significantly with lab estimates, which assumed a 75% reduction in emissions.

Analysts studied information from in-vehicle energy use monitors of eight hundred thousand vehicles registered in the EU between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab figures, up from three and a half times in 2021.

“Real-world CO2 output are increasing, while lab-reported figures are falling,” said a senior researcher participating in the report. “That discrepancy is growing and creates a significant issue. Consequently, PHEVs pollute nearly as much as gasoline cars.”

Key Factors Behind the Discrepancy

Analysts linked most of the gap to inflated estimates of the “electric driving share” – the percentage of miles travelled in electric mode relative to total distance. They found that just a quarter of driving was done in electric mode, while lab estimates suggested over four-fifths.

Even, when running in EV mode, pollution amounts were well above lab projections. That occurred because electric motors were not strong sufficient to function independently, leading to engines using gasoline for almost a third of the distance covered in EV mode.

Policy and Economic Consequences

According to estimates, the underestimation of PHEV emissions enabled four major carmaker companies to avoid over €5bn in penalties between 2021 and 2023, by falsely easing adherence with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs would spend approximately €500 more per year in running costs than would be assumed under laboratory tests.

“The bold claims that manufacturers like to make about their PHEV vehicles are clearly way off the truth,” stated a automotive analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are little improved than regular gas and diesel cars in terms of energy consumption, CO₂ production, and running expenses.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid cars have recently been brought back into political discussions as automakers have lobbied the European Union to weaken CO₂ targets. A planned ban on new internal combustion vehicles in 2035 has faced intense pressure from the automotive sector and resistance from member states with significant car industries.

Some high-level officials have proposed PHEVs as a possible “flexibility” solution to include in the legislation.

An external energy economics expert, who was not involved with the study, described the report a “highly valuable addition” after years in which segments of the automotive industry argued there was insufficient information to properly evaluate actual CO2 output.

“These findings show, beyond any doubt, that the gap in lab and actual PHEV fuel consumption and CO₂ output is much, much larger than for petrol or conventional vehicles,” the expert said. “Any policy adjustments concerning PHEVs should be made with extreme caution and in the light of that evidence.”