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PHEVs emit nearly 5x more planet-heating pollution than official figures show, according to a new analysis.

Growing Gap In Official and Actual Emissions

Data shows that PHEVs release just one-fifth less CO₂ than traditional gas and diesel vehicles, based on research carried out by a advocacy group. This contrasts significantly with lab tests, which suggested a 75% decrease in pollution.

Researchers examined data from onboard energy use monitors of 800,000 cars sold in the EU between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, increased from three and a half times in 2021.

“Actual emissions are increasing, while official figures are decreasing,” said a lead researcher participating in the study. “This gap is growing and creates a significant problem. As a result, PHEVs pollute nearly as much as petrol vehicles.”

Key Reasons Driving the Emissions Gap

Researchers linked the majority of the difference to inflated estimates of the “electric driving share” – the percentage of miles travelled in battery power compared to total distance. They determined that just a quarter of travel was completed in electric mode, whereas official estimates suggested over four-fifths.

Additionally, when running in EV mode, pollution levels were well above lab estimates. That happened because electric motors were not strong enough to function alone, resulting to engines burning gasoline for nearly a third of the travel covered in EV mode.

Policy and Financial Implications

According to estimates, the underestimation of PHEV CO2 output allowed several large carmaker groups to escape more than €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could spend about €500 more annually in operating costs than would be estimated under lab conditions.

“The strong statements that automakers often promote about their plug-in hybrid vehicles are obviously way off the mark,” stated a automotive analyst. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are only slightly improved than standard gas and diesel cars in terms of fuel use, CO₂ production, and operating expenses.”

Policy Discussion and Industry Lobbying

Plug-in hybrid vehicles have lately been drawn again into political debates as carmakers have lobbied the EU to weaken CO₂ standards. A planned prohibition on sales of new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive industry and opposition from EU countries with significant automotive industries.

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

One independent energy policy expert, who was unaffiliated with the study, described the analysis a “very useful contribution” after a long period in which parts of the automotive sector claimed there was insufficient information to accurately evaluate actual CO2 output.

“These findings show, without question, that the difference between official and real-world PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or conventional vehicles,” they said. “All policy adjustments concerning PHEVs should be made with extreme care and considering this evidence.”