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Plug-in hybrid electric vehicles produce almost 5x more global warming pollution than official figures show, according to a recent analysis.

Widening Discrepancy Between Lab and Actual CO2 Output

Data shows that PHEVs release only one-fifth less CO₂ than traditional petrol and diesel vehicles, according to research carried out by a non-profit group. This differs sharply with laboratory estimates, which assumed a 75% decrease in emissions.

Researchers examined data from onboard fuel consumption meters of eight hundred thousand cars registered in the EU from 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, increased from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported figures are decreasing,” stated a senior analyst participating in the report. “This gap is widening and creates a serious issue. As a result, PHEVs emit almost as much as petrol vehicles.”

Key Factors Behind the Discrepancy

Analysts linked most of the difference to inflated estimates of the “utility factor” – the percentage of miles travelled in electric power compared to overall mileage. The team found that just a quarter of driving was completed in EV mode, whereas official assumptions assumed 84%.

Additionally, when running in EV mode, emission levels were well above lab projections. That happened because EV motors were insufficiently powerful enough to operate independently, leading to engines using gasoline for nearly a third of the distance covered in EV mode.

Policy and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output enabled several large carmaker groups to escape over €5bn in penalties from 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ targets.

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

“The bold statements that automakers often promote about their plug-in hybrid cars are obviously way off the mark,” stated a transport analyst. “Buyers are being duped into believing that by buying a PHEV, they are helping the environment and saving money. Actually, PHEVs are little improved than standard petrol and diesel cars in terms of energy consumption, CO₂ emissions, and running expenses.”

Political Debate and Automotive Pressure

Plug-in hybrid vehicles have lately been brought again into policy discussions as automakers have pressed the European Union to weaken CO₂ standards. A proposed prohibition on sales of new combustion engine cars in 2035 has faced intense pressure from the automotive industry and resistance from member states with large car industries.

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

One external energy economics expert, who was not involved with the study, called the report a “highly valuable contribution” after a long period in which segments of the car industry argued there was too little data to accurately evaluate actual CO2 output.

“The results show, without question, that the difference between lab and actual PHEV energy use and CO₂ output is much, much greater than for petrol or conventional cars,” the expert said. “Any policy adjustments regarding PHEVs should be made with utmost caution and in the light of this evidence.”