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Plug-in hybrid cars produce almost five times more global warming emissions than lab-reported figures show, according to a new analysis.

Growing Gap Between Lab and Real-World CO2 Output

Data reveals that PHEVs emit only 19% lower CO₂ than traditional gas and diesel vehicles, based on research conducted by a non-profit organization. This differs significantly with lab estimates, which assumed a three-quarters reduction in emissions.

Analysts examined information from in-vehicle energy use meters of 800,000 cars sold in Europe from 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, up from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported emissions are falling,” said a senior researcher involved in the report. “This discrepancy is growing and poses a significant issue. Consequently, PHEVs pollute almost as heavily as gasoline vehicles.”

Key Reasons Behind the Emissions Gap

Analysts linked the majority of the difference to inflated estimates of the “electric driving share” – the percentage of miles driven in electric mode compared to overall distance. They found that only 27% of travel was completed in electric mode, whereas lab assumptions assumed over four-fifths.

Additionally, when running in EV mode, emission levels were well above official estimates. That occurred because EV motors were not strong sufficient to operate alone, resulting to engines burning fossil fuels for nearly one-third of the travel completed in electric mode.

Policy and Financial Implications

Based on estimates, the underestimation of PHEV CO2 output allowed four major carmaker companies to avoid more than €5bn in penalties from 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would spend approximately €500 extra per year in operating expenses than would be assumed under laboratory conditions.

“The bold statements that automakers like to make about their PHEV cars are clearly way off the mark,” stated a transport expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and cutting money. Actually, PHEVs are only slightly better than standard gas and diesel cars in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Political Debate and Industry Pressure

Hybrid vehicles have recently been brought back into political discussions as carmakers have lobbied the EU to weaken CO₂ targets. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the automotive industry and opposition from EU countries with large car industries.

Some senior politicians have proposed plug-in hybrids as a possible “flexibility” option to include in the legislation.

An 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 information to accurately assess real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the difference between lab and real-world PHEV fuel consumption and CO₂ emissions is much, much greater than for gasoline or diesel cars,” they stated. “Any regulatory changes regarding PHEVs should be implemented with extreme caution and in the light of that evidence.”