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Plug-in hybrid electric vehicles release almost 5x more global warming pollution than lab-reported figures indicate, according to a new analysis.

Widening Gap In Lab and Actual CO2 Output

Statistics shows that PHEVs release only one-fifth lower CO₂ than traditional petrol and diesel cars, based on research carried out by a advocacy group. This contrasts sharply with laboratory tests, which suggested a three-quarters reduction in pollution.

Researchers examined data from onboard energy use meters of eight hundred thousand vehicles registered in the EU between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are decreasing,” said a senior researcher participating in the report. “This gap is widening and creates a significant issue. As a result, PHEVs pollute nearly as much as gasoline cars.”

Primary Factors Driving the Emissions Gap

Researchers attributed most of the difference to overestimates of the “utility factor” – the ratio of kilometers travelled in battery power relative to total mileage. The team found that just 27% of travel was completed in electric mode, while lab estimates suggested over four-fifths.

Even, when operating in EV mode, pollution amounts were well above official estimates. This occurred because electric motors were not strong sufficient to function independently, leading to combustion motors using gasoline for almost one-third of the distance covered in electric mode.

Regulatory and Economic Implications

According to estimates, the lowballing of PHEV emissions allowed four large automaker companies to avoid over €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs would pay approximately €500 extra per year in operating costs than is estimated under lab tests.

“The bold statements that automakers like to make about their PHEV vehicles are clearly far from the mark,” stated a automotive analyst. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are only slightly better than standard gas and diesel vehicles in terms of fuel use, CO₂ emissions, and running expenses.”

Policy Debate and Automotive Lobbying

Plug-in hybrid cars have recently been drawn again into political debates as automakers have lobbied the European Union to weaken CO₂ standards. A planned ban on new internal combustion vehicles in 2035 has faced heavy lobbying from the car industry and opposition from member states with significant car manufacturing.

Some senior officials have suggested plug-in hybrids as a possible “flexibility” solution to introduce in the regulation.

An independent energy economics expert, who was not involved with the research, called the report a “very useful addition” after years in which parts of the automotive industry claimed there was insufficient data to accurately assess actual emissions.

“These findings show, beyond any doubt, that the gap between lab and actual PHEV fuel consumption and CO₂ emissions is significantly greater than for gasoline or diesel vehicles,” the expert said. “All regulatory changes regarding PHEVs should be made with extreme care and considering this data.”