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Plug-in hybrid cars produce nearly five times greater planet-heating emissions than lab-reported data show, according to a new report.

Widening Gap In Lab and Actual Emissions

Statistics reveals that PHEVs release just one-fifth lower CO₂ than conventional petrol and diesel vehicles, according to analysis carried out by a non-profit group. This contrasts significantly with lab tests, which suggested a three-quarters reduction in emissions.

Analysts examined data from onboard fuel consumption monitors of eight hundred thousand vehicles sold in Europe between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while official emissions are decreasing,” stated a senior researcher involved in the study. “That gap is widening and creates a serious problem. Consequently, PHEVs emit almost as heavily as petrol cars.”

Primary Reasons Behind the Discrepancy

Researchers attributed most of the difference to inflated estimates of the “utility factor” – the ratio of miles driven in electric power compared to total distance. The team determined that only a quarter of driving was completed in EV mode, while official estimates assumed 84%.

Additionally, when running in electric mode, pollution amounts were significantly higher than lab projections. That happened because electric motors were insufficiently powerful enough to function alone, leading to engines burning gasoline for nearly a third of the travel completed in electric mode.

Policy and Financial Consequences

According to estimates, the lowballing of PHEV CO2 output enabled four large automaker groups to avoid more than €5bn in fines from 2021 and 2023, by falsely easing adherence with European Union fleet-average CO₂ standards.

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

“The strong statements that manufacturers like to make about their plug-in hybrid cars are obviously way off the mark,” stated a automotive analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are helping the environment and cutting money. Actually, PHEVs are little better than regular petrol and diesel cars in terms of fuel use, CO₂ production, and operating expenses.”

Political Debate and Automotive Pressure

Hybrid vehicles have recently been drawn again into political debates as carmakers have lobbied the European Union to relax CO₂ standards. A planned ban on new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive industry and opposition from member states with large car manufacturing.

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

One external energy economics expert, who was unaffiliated with the study, called the report a “highly valuable addition” after years in which parts of the car sector claimed there was insufficient data to properly assess real-world emissions.

“These findings demonstrate, without question, that the gap between official and real-world PHEV energy use and CO₂ output is significantly greater than for gasoline or conventional vehicles,” the expert said. “All policy adjustments regarding PHEVs should be made with utmost caution and considering that evidence.”