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Plug-in hybrid electric vehicles produce almost 5x more global warming emissions than lab-reported figures indicate, as per a recent report.

Growing Gap Between Official and Real-World CO2 Output

Data reveals that PHEVs release only one-fifth lower CO₂ than conventional petrol and diesel cars, based on research conducted by a non-profit group. That differs significantly with lab estimates, which suggested a 75% decrease in emissions.

Analysts studied information from onboard energy use meters of 800,000 cars registered in Europe from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than official figures, up from 3.5 times in 2021.

“Actual CO2 output are increasing, while official figures are decreasing,” said a senior analyst participating in the study. “This gap is widening and creates a serious issue. As a result, PHEVs emit almost as heavily as petrol vehicles.”

Key Factors Driving the Emissions Gap

Researchers attributed the majority of the gap to overestimates of the “utility factor” – the percentage of kilometers driven in electric power relative to overall distance. They found that just 27% of travel was completed in electric mode, whereas lab assumptions assumed 84%.

Additionally, when running in EV mode, emission amounts were well above lab projections. That happened because electric motors were not strong sufficient to operate independently, resulting to engines using gasoline for almost one-third of the travel completed in EV mode.

Regulatory and Economic Consequences

According to estimates, the lowballing of PHEV CO2 output allowed four large carmaker groups to escape over €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ standards.

Additionally, owners of PHEVs would spend approximately €500 more annually in operating expenses than would be assumed under lab tests.

“The bold statements that manufacturers often promote about their PHEV vehicles are clearly way off the truth,” commented a transport expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are little improved than regular petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and operating costs.”

Policy Debate and Industry Lobbying

Plug-in hybrid vehicles have recently been brought back into political discussions as automakers have pressed the EU to weaken CO₂ targets. A proposed prohibition on new internal combustion vehicles in 2035 has faced intense pressure from the automotive sector and opposition from EU countries with large car industries.

Several high-level politicians have proposed PHEVs as a potential “compromise” option to introduce in the regulation.

An external energy policy specialist, who was not involved with the research, called the report a “highly valuable addition” after a long period in which segments of the automotive sector argued there was too little information to accurately assess real-world CO2 output.

“These findings demonstrate, without question, that the difference in lab and real-world PHEV energy use and CO₂ emissions is much, much greater than for petrol or conventional vehicles,” the expert said. “Any regulatory adjustments regarding PHEVs should be made with utmost care and in the light of this data.”