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Plug-in hybrid electric vehicles emit almost 5x more global warming emissions than lab-reported figures show, according to a new report.

Widening Gap Between Lab and Real-World CO2 Output

Statistics shows that PHEVs emit just 19% less CO₂ than conventional petrol and diesel cars, based on research carried out by a advocacy group. This differs sharply with laboratory tests, which assumed a 75% reduction in emissions.

Researchers examined data from in-vehicle fuel consumption meters of 800,000 vehicles sold in Europe from 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, increased from three and a half times in 2021.

“Actual CO2 output are increasing, while official emissions are decreasing,” said a senior analyst participating in the report. “This discrepancy is growing and creates a significant issue. As a result, PHEVs emit nearly as much as gasoline vehicles.”

Key Factors Driving the Discrepancy

Researchers linked most of the gap to overestimates of the “utility factor” – the ratio of kilometers driven in battery power compared to total distance. The team determined that just 27% of driving was done in electric mode, whereas official assumptions assumed 84%.

Additionally, when operating in EV mode, emission amounts were significantly higher than lab estimates. That occurred because electric motors were not strong sufficient to function independently, leading to engines burning fossil fuels for nearly a third of the distance covered in EV mode.

Policy and Financial Implications

Based on calculations, the lowballing of PHEV CO2 output allowed four major automaker groups to avoid more than €5bn in penalties from 2021 and 2023, by falsely easing compliance with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs would spend about €500 extra annually in running costs than is estimated under laboratory conditions.

“The strong claims that automakers like to make about their PHEV vehicles are obviously way off the mark,” stated a transport expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and cutting costs. In reality, PHEVs are little better than standard petrol and diesel cars in terms of energy use, CO₂ production, and operating costs.”

Political Discussion and Automotive Lobbying

Hybrid cars have recently been drawn again into political discussions as automakers have lobbied the European Union to weaken CO₂ standards. A planned ban on new internal combustion cars in 2035 has faced heavy pressure from the automotive industry and resistance from member states with significant automotive industries.

Several high-level politicians have proposed plug-in hybrids as a potential “flexibility” option to introduce in the legislation.

An external energy policy specialist, who was not involved with the research, described the report a “highly valuable addition” after a long period in which parts of the car sector claimed there was insufficient data to accurately assess real-world emissions.

“These findings demonstrate, beyond any doubt, that the gap between official and real-world PHEV fuel consumption and CO₂ emissions is significantly greater than for gasoline or diesel vehicles,” they stated. “All policy changes concerning PHEVs should be implemented with utmost care and in the light of this data.”