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Plug-in hybrid cars emit nearly five times more planet-heating pollution than official figures indicate, according to a recent report.

Growing Gap Between Official and Real-World CO2 Output

Statistics shows that PHEVs release just 19% lower CO₂ than conventional petrol and diesel cars, according to analysis carried out by a non-profit organization. This differs sharply with laboratory estimates, which assumed a three-quarters decrease in emissions.

Researchers examined data from in-vehicle energy use monitors of 800,000 cars sold in Europe from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, up from three and a half times in 2021.

“Actual emissions are increasing, while official figures are falling,” said a lead analyst participating in the report. “This gap is widening and creates a significant issue. Consequently, PHEVs pollute nearly as heavily as petrol cars.”

Key Reasons Driving the Emissions Gap

Analysts attributed most of the difference to inflated estimates of the “utility factor” – the percentage of kilometers driven in electric power compared to total distance. The team determined that only 27% of travel was completed in electric mode, whereas lab assumptions suggested 84%.

Even, when operating in EV mode, emission amounts were significantly higher than official projections. That happened because electric motors were insufficiently powerful sufficient to function independently, leading to combustion motors using fossil fuels for nearly a third of the travel completed in EV mode.

Regulatory and Economic Implications

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

Furthermore, owners of PHEVs would spend about €500 extra annually in operating costs than would be assumed under lab conditions.

“The bold statements that automakers often promote about their plug-in hybrid cars are clearly way off the truth,” commented a automotive expert. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are little improved than standard petrol and diesel vehicles in terms of energy use, CO₂ production, and running costs.”

Political Discussion and Industry Pressure

Plug-in hybrid cars have recently been drawn again into policy debates as automakers have lobbied the European Union to weaken CO₂ standards. A proposed ban on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the automotive sector and opposition from EU countries with large car manufacturing.

Several senior politicians have suggested plug-in hybrids as a possible “flexibility” option to introduce in the regulation.

An external energy policy specialist, who was not involved with the research, called the analysis a “highly valuable addition” after years in which segments of the automotive industry claimed there was insufficient data to properly assess actual emissions.

“The results demonstrate, without question, that the difference between lab and actual PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or conventional vehicles,” they stated. “Any policy adjustments regarding PHEVs should be made with extreme caution and in the light of that data.”