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Plug-in hybrid electric vehicles emit almost 5x greater planet-heating pollution than official data show, according to a new analysis.

Widening Gap In Official and Actual CO2 Output

Statistics reveals that PHEVs release just 19% lower CO₂ than conventional gas and diesel cars, according to research conducted by a non-profit organization. That differs significantly with laboratory estimates, which assumed a three-quarters reduction in pollution.

Analysts studied data from in-vehicle energy use meters of 800,000 cars registered in Europe between 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab figures, increased from three and a half times in 2021.

“Actual emissions are increasing, while official emissions are decreasing,” said a senior researcher involved in the report. “That discrepancy is growing and poses a significant problem. As a result, PHEVs emit nearly as heavily as gasoline vehicles.”

Key Reasons Behind the Discrepancy

Researchers linked the majority of the difference to overestimates of the “utility factor” – the percentage of kilometers driven in battery power compared to overall mileage. They found that just a quarter of driving was done in EV mode, whereas lab estimates assumed 84%.

Additionally, when running in EV mode, pollution levels were well above official projections. This happened because EV motors were insufficiently powerful enough to operate independently, leading to combustion motors using fossil fuels for nearly one-third of the distance covered in EV mode.

Policy and Financial Consequences

According to estimates, the underestimation of PHEV CO2 output allowed four major carmaker companies to avoid over €5bn in penalties from 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs would spend approximately €500 extra annually in running expenses than would be estimated under lab conditions.

“The strong statements that automakers like to make about their PHEV cars are obviously way off the mark,” commented 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 better than regular gas and diesel vehicles in terms of energy consumption, CO₂ emissions, and running expenses.”

Political Discussion and Industry Pressure

Hybrid cars have recently been drawn again into political debates as automakers have lobbied the EU to relax CO₂ standards. A proposed prohibition on sales of new internal combustion cars in 2035 has faced heavy lobbying from the automotive industry and opposition from member states with large car manufacturing.

Several senior officials have proposed plug-in hybrids as a possible “compromise” option to include in the legislation.

One external energy economics expert, who was not involved with the research, called the analysis a “highly valuable contribution” after years in which parts of the automotive sector claimed there was too little information to accurately evaluate actual CO2 output.

“These findings demonstrate, beyond any doubt, that the difference between official and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for petrol or diesel vehicles,” they stated. “Any regulatory adjustments regarding PHEVs should be made with extreme care and in the light of this data.”