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Plug-in hybrid cars produce almost 5x more global warming pollution than lab-reported data show, according to a recent report.

Widening Discrepancy Between Official and Actual Emissions

Statistics reveals that PHEVs emit only one-fifth lower CO₂ than traditional petrol and diesel cars, based on analysis conducted by a non-profit group. This contrasts significantly with lab estimates, which suggested a 75% reduction in pollution.

Researchers studied information from in-vehicle fuel consumption meters of 800,000 vehicles registered in Europe from 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than official estimates, increased from three and a half times in 2021.

“Actual emissions are rising, while lab-reported emissions are decreasing,” said a senior researcher involved in the study. “This discrepancy is widening and creates a serious problem. Consequently, PHEVs emit nearly as heavily as petrol cars.”

Key Factors Driving the Discrepancy

Analysts linked the majority of the gap to overestimates of the “electric driving share” – the percentage of kilometers driven in electric power relative to total mileage. The team determined that only a quarter of driving was done in EV mode, while lab assumptions assumed 84%.

Additionally, when operating in electric mode, emission levels were significantly higher than official projections. This happened because electric motors were insufficiently powerful enough to function independently, resulting to engines using fossil fuels for almost a third of the travel completed in electric mode.

Regulatory and Financial Consequences

Based on calculations, the lowballing of PHEV emissions enabled four major automaker groups to avoid over €5bn in penalties between 2021 and 2023, by artificially easing adherence with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs could spend about €500 more per year in running expenses than is assumed under laboratory tests.

“The strong statements that manufacturers often promote about their plug-in hybrid cars are clearly far from the truth,” commented a transport expert. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are only slightly improved than regular petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and operating expenses.”

Political Debate and Automotive Lobbying

Hybrid cars have lately been brought back into political debates as automakers have lobbied the European Union to relax CO₂ standards. A planned ban on new combustion engine vehicles in 2035 has faced heavy pressure from the car sector and opposition from EU countries with significant automotive industries.

Some senior politicians have proposed plug-in hybrids as a potential “compromise” solution to introduce in the legislation.

One independent energy economics specialist, who was unaffiliated with the study, called the report a “highly valuable addition” after years in which parts of the automotive industry argued there was insufficient information to properly assess real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the gap between official and real-world PHEV energy use and CO₂ output is much, much larger than for gasoline or conventional vehicles,” the expert said. “All regulatory adjustments concerning PHEVs should be implemented with extreme caution and considering this data.”