Plug in Hybrid Vehicles Pollute Almost as Heavily as Petrol Cars, Study Finds

PHEVs produce almost five times greater planet-heating emissions than official data show, according to a new report.

Growing Discrepancy In Lab and Real-World Emissions

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

Analysts examined information from onboard fuel consumption meters of eight hundred thousand cars registered in Europe from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, increased from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are decreasing,” said a lead researcher participating in the study. “That discrepancy is growing and creates a significant problem. As a result, PHEVs emit nearly as much as gasoline vehicles.”

Primary Factors Behind the Discrepancy

Analysts attributed most of the gap to overestimates of the “utility factor” – the ratio of kilometers travelled in electric mode compared to total mileage. The team found that just a quarter of driving was completed in EV mode, whereas lab assumptions assumed 84%.

Additionally, when operating in EV mode, emission levels were well above lab estimates. This occurred because electric motors were not strong sufficient to function independently, leading to engines burning fossil fuels for almost one-third of the travel covered in electric mode.

Regulatory and Economic Implications

According to calculations, the underestimation of PHEV CO2 output enabled several large carmaker groups to escape over €5bn in penalties between 2021 and 2023, by artificially easing compliance with EU average fleet CO₂ targets.

Furthermore, drivers of PHEVs could pay approximately €500 extra annually in operating costs than is estimated under lab conditions.

“The bold claims that automakers often promote about their PHEV cars are clearly far from the mark,” commented a transport expert. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are little better than regular petrol and diesel cars in terms of energy consumption, CO₂ emissions, and running costs.”

Political Discussion and Industry Pressure

Hybrid vehicles have recently been drawn back into policy debates as carmakers have lobbied the European Union to relax CO₂ standards. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the automotive industry and resistance from EU countries with significant car manufacturing.

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

One independent energy policy specialist, who was unaffiliated with the study, called the analysis a “very useful contribution” after a long period in which segments of the car sector argued there was too little data to properly evaluate real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the gap in official and actual PHEV energy use and CO₂ emissions is significantly greater than for gasoline or conventional cars,” they said. “Any policy changes regarding PHEVs should be made with utmost caution and considering this data.”