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Plug-in hybrid electric vehicles emit nearly 5x greater global warming pollution than lab-reported figures show, according to a recent report.

Widening Gap In Official and Actual CO2 Output

Statistics shows that PHEVs emit just one-fifth lower CO₂ than conventional petrol and diesel vehicles, based on research carried out by a advocacy organization. This contrasts sharply with laboratory tests, which suggested a three-quarters reduction in emissions.

Analysts studied information from onboard fuel consumption meters of 800,000 cars registered in Europe between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while official emissions are falling,” said a lead researcher participating in the report. “This discrepancy is widening and creates a serious issue. Consequently, PHEVs pollute nearly as heavily as petrol cars.”

Primary Factors Driving the Emissions Gap

Researchers attributed most of the difference to overestimates of the “electric driving share” – the ratio of kilometers driven in battery mode compared to overall mileage. The team found that just a quarter of driving was done in electric mode, while official assumptions assumed over four-fifths.

Additionally, when operating in EV mode, emission levels were well above official estimates. That happened because electric motors were insufficiently powerful sufficient to function independently, resulting to engines using gasoline for almost one-third of the distance completed in EV mode.

Policy and Financial Consequences

Based on estimates, the underestimation of PHEV CO2 output allowed several large carmaker groups to escape more than €5bn in penalties from 2021 and 2023, by falsely easing compliance with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs would pay approximately €500 extra per year in running costs than is estimated under lab tests.

“The bold statements that manufacturers often promote about their plug-in hybrid cars are clearly way off the mark,” stated a transport expert. “Consumers are being duped into believing that by buying a PHEV, they are helping the planet and cutting money. In reality, PHEVs are only slightly better than standard gas and diesel vehicles in terms of energy use, CO₂ emissions, and operating expenses.”

Political Discussion and Industry Pressure

Hybrid cars have lately been drawn again into political debates as automakers have pressed the EU to weaken CO₂ standards. A proposed prohibition on new combustion engine cars in 2035 has faced heavy pressure from the automotive industry and opposition from member states with large car industries.

Some high-level officials have suggested plug-in hybrids as a potential “compromise” solution to include in the regulation.

One independent energy economics expert, who was unaffiliated with the research, described the report a “highly valuable contribution” after a long period in which parts of the car sector claimed there was too little information to properly evaluate actual CO2 output.

“The results show, without question, that the gap in lab and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or conventional vehicles,” they stated. “Any policy adjustments concerning PHEVs should be implemented with utmost caution and considering that data.”