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Plug-in hybrid cars release almost 5x greater planet-heating pollution than official figures indicate, according to a new analysis.

Widening Discrepancy Between Lab and Real-World CO2 Output

Statistics reveals that PHEVs release only one-fifth lower CO₂ than conventional petrol and diesel vehicles, according to analysis carried out by a non-profit group. That differs sharply with laboratory tests, which assumed a three-quarters reduction in pollution.

Researchers studied information from onboard fuel consumption monitors of eight hundred thousand cars sold in Europe between 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times higher than official figures, increased from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported figures are falling,” said a senior analyst participating in the report. “This gap is growing and creates a serious issue. As a result, PHEVs emit almost as much as petrol vehicles.”

Key Factors Behind the Discrepancy

Researchers linked the majority of the difference to inflated estimates of the “utility factor” – the ratio of kilometers travelled in electric mode compared to total distance. The team determined that just a quarter of driving was completed in EV mode, while lab assumptions assumed over four-fifths.

Even, when operating in EV mode, pollution levels were well above official projections. That occurred because EV motors were not strong enough to operate independently, leading to engines burning gasoline for nearly a third of the distance completed in electric mode.

Regulatory and Financial Implications

Based on estimates, the lowballing of PHEV emissions allowed four major carmaker companies to avoid more than €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could spend approximately €500 extra annually in running costs than would be estimated under laboratory tests.

“The strong claims that automakers like to make about their plug-in hybrid cars are obviously way off the mark,” commented a transport expert. “Consumers are being duped into thinking that by buying a PHEV, they are helping the planet and saving costs. In reality, PHEVs are only slightly better than regular gas and diesel cars in terms of energy use, CO₂ production, and operating costs.”

Political Debate and Industry Lobbying

Hybrid vehicles have lately been drawn back into policy discussions as carmakers have lobbied the European Union to weaken CO₂ targets. A proposed ban on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the automotive industry and opposition from member states with significant car manufacturing.

Some high-level politicians have proposed plug-in hybrids as a possible “compromise” solution to include in the legislation.

An external energy policy specialist, who was unaffiliated with the study, called the report a “highly valuable addition” after a long period in which segments of the automotive industry claimed there was insufficient information to properly evaluate real-world emissions.

“The results demonstrate, without question, that the difference between lab and real-world PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or diesel cars,” the expert stated. “Any policy changes regarding PHEVs should be implemented with utmost caution and in the light of that evidence.”