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PHEVs release nearly five times more planet-heating pollution than official data indicate, according to a new analysis.

Widening Gap Between Lab and Actual CO2 Output

Statistics reveals that PHEVs release just 19% less CO₂ than conventional gas and diesel vehicles, based on analysis conducted by a advocacy organization. This differs sharply with lab tests, which assumed a three-quarters decrease in emissions.

Analysts studied information from onboard energy use monitors of eight hundred thousand cars registered in the EU from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than lab estimates, up from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported emissions are decreasing,” said a lead researcher involved in the study. “This discrepancy is widening and poses a significant problem. Consequently, PHEVs pollute almost as heavily as petrol cars.”

Primary Factors Driving the Discrepancy

Researchers linked most of the difference to inflated estimates of the “electric driving share” – the percentage of miles driven in battery power compared to overall distance. The team determined that only 27% of driving was done in electric mode, whereas official assumptions suggested 84%.

Even, when running in electric mode, pollution amounts were significantly higher than official estimates. That occurred because electric motors were not strong enough to function alone, leading to engines burning fossil fuels for almost one-third of the travel covered in EV mode.

Policy and Economic Implications

Based on estimates, the lowballing of PHEV CO2 output enabled several major automaker groups to escape over €5bn in fines between 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs could pay about €500 extra per year in running costs than would be estimated under laboratory tests.

“The strong statements that automakers like to make about their plug-in hybrid cars are clearly way off the mark,” commented a automotive analyst. “Consumers are being misled into thinking that by purchasing a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are little better than standard gas and diesel vehicles in terms of energy use, CO₂ emissions, and operating costs.”

Political Debate and Industry Pressure

Plug-in hybrid cars have lately been drawn back into policy discussions as automakers have pressed the European Union to weaken CO₂ standards. A planned ban on new internal combustion cars in 2035 has faced intense pressure from the automotive industry and opposition from EU countries with significant car manufacturing.

Some senior officials have proposed PHEVs as a potential “flexibility” solution to include in the regulation.

An external energy policy expert, who was unaffiliated with the study, called the report a “highly valuable addition” after a long period in which parts of the car sector argued there was too little information to properly evaluate real-world emissions.

“The results demonstrate, beyond any doubt, that the difference in lab and actual PHEV energy use and CO₂ output is significantly greater than for petrol or diesel cars,” they stated. “All regulatory changes regarding PHEVs should be made with utmost care and in the light of this data.”