Plug-in Hybrid Cars Pollute Almost as Heavily as Gasoline Cars, Study Finds

Plug-in hybrid electric vehicles emit almost five times more planet-heating emissions than lab-reported data indicate, according to a recent report.

Growing Discrepancy Between Official and Real-World Emissions

Statistics reveals that PHEVs release only 19% less CO₂ than conventional gas and diesel cars, based on analysis carried out by a non-profit group. That contrasts sharply with laboratory estimates, which suggested a three-quarters decrease in emissions.

Researchers examined data from onboard energy use monitors of 800,000 cars registered in the EU from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, up from three and a half times in 2021.

“Real-world emissions are rising, while official figures are falling,” said a senior analyst involved in the study. “That gap is growing and creates a serious problem. As a result, PHEVs emit almost as heavily as gasoline vehicles.”

Primary Factors Driving the Emissions Gap

Researchers linked most of the gap to overestimates of the “utility factor” – the ratio of miles driven in electric power relative to total mileage. They found that just 27% of travel was completed in EV mode, whereas lab assumptions suggested over four-fifths.

Even, when running in electric mode, emission levels were significantly higher than lab projections. That occurred because EV motors were not strong sufficient to function alone, resulting to engines using gasoline for almost one-third of the distance completed in EV mode.

Regulatory and Economic Consequences

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

Furthermore, drivers of PHEVs could spend about €500 more per year in operating costs than would be estimated under lab conditions.

“The bold claims that automakers like to make about their plug-in hybrid vehicles are clearly far from the truth,” stated a transport analyst. “Consumers are being misled into thinking that by buying a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are only slightly better than regular petrol and diesel cars in terms of fuel consumption, CO₂ production, and operating expenses.”

Political Debate and Industry Pressure

Hybrid vehicles have lately been brought again into political discussions as carmakers have pressed the European Union to weaken CO₂ standards. A proposed ban on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the car industry and resistance from EU countries with significant car industries.

Some senior officials have suggested PHEVs as a possible “flexibility” option to introduce in the legislation.

An independent energy policy expert, who was unaffiliated with the study, described the report a “highly valuable addition” after a long period in which segments of the automotive industry claimed there was too little information to properly evaluate actual emissions.

“These findings demonstrate, without question, that the gap between official and real-world PHEV energy use and CO₂ emissions is significantly larger than for gasoline or diesel vehicles,” the expert said. “All policy changes concerning PHEVs should be implemented with utmost caution and in the light of that data.”