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Plug-in hybrid cars emit almost 5x greater planet-heating emissions than official figures show, according to a new analysis.

Growing Gap In Official and Real-World Emissions

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

Analysts studied information from in-vehicle energy use monitors of eight hundred thousand cars registered in Europe from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, up from three and a half times in 2021.

“Actual emissions are rising, while official emissions are decreasing,” stated a lead researcher participating in the report. “That discrepancy is growing and poses a serious issue. Consequently, PHEVs pollute nearly as heavily as gasoline cars.”

Key Reasons Behind the Emissions Gap

Researchers linked the majority of the difference to inflated estimates of the “utility factor” – the percentage of kilometers driven in electric mode compared to overall mileage. They determined that just 27% of travel was done in electric mode, while lab assumptions suggested over four-fifths.

Even, when operating in electric mode, emission levels were significantly higher than lab estimates. That happened because EV motors were insufficiently powerful sufficient to function alone, leading to engines burning gasoline for nearly one-third of the distance completed in EV mode.

Regulatory and Economic Consequences

Based on estimates, the underestimation of PHEV CO2 output enabled several large automaker companies to avoid over €5bn in penalties from 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs would spend approximately €500 more per year in operating costs than is assumed under lab conditions.

“The strong statements that manufacturers often promote about their PHEV cars are obviously way off the mark,” commented a transport analyst. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are little better than regular petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and operating costs.”

Political Debate and Automotive Lobbying

Hybrid vehicles have recently been drawn again into political debates as automakers have lobbied the European Union to weaken CO₂ standards. A planned prohibition on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the car industry and resistance from EU countries with large car manufacturing.

Several senior politicians have suggested PHEVs as a possible “flexibility” option to introduce in the regulation.

An independent energy policy expert, who was not involved with the study, described the report a “highly valuable contribution” after years in which segments of the automotive sector claimed there was insufficient information to accurately assess actual emissions.

“The results show, beyond any doubt, that the difference in lab and real-world PHEV energy use and CO₂ output is much, much greater than for gasoline or diesel cars,” they said. “Any regulatory changes concerning PHEVs should be implemented with extreme caution and considering that evidence.”