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Plug-in hybrid electric vehicles release nearly five times more global warming pollution than official figures indicate, according to a recent analysis.

Growing Discrepancy Between Lab and Real-World Emissions

Statistics shows that PHEVs emit only 19% less CO₂ than traditional gas and diesel cars, according to research carried out by a non-profit group. This differs sharply with laboratory estimates, which assumed a three-quarters reduction in emissions.

Analysts examined information from in-vehicle fuel consumption meters of 800,000 cars registered in the EU between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are falling,” stated a senior analyst involved in the report. “That gap is widening and poses a serious issue. As a result, PHEVs pollute nearly as much as gasoline vehicles.”

Primary Reasons Behind the Discrepancy

Researchers linked the majority of the gap to overestimates of the “utility factor” – the percentage of kilometers driven in electric mode compared to overall mileage. They found that only a quarter of travel was done in EV mode, whereas lab assumptions suggested over four-fifths.

Additionally, when running in electric mode, pollution levels were well above official projections. This happened because EV motors were not strong enough to operate independently, leading to combustion motors burning fossil fuels for nearly one-third of the distance covered in electric mode.

Policy and Financial Implications

Based on estimates, the lowballing of PHEV CO2 output allowed four large automaker companies to avoid over €5bn in penalties from 2021 and 2023, by artificially easing adherence with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs would spend about €500 extra annually in running expenses than is estimated under laboratory tests.

“The bold statements that manufacturers often promote about their PHEV vehicles are obviously way off the mark,” stated a transport analyst. “Buyers are being misled into thinking that by buying a PHEV, they are helping the planet and cutting costs. In reality, PHEVs are little improved than standard petrol and diesel vehicles in terms of energy consumption, CO₂ production, and operating costs.”

Political Debate and Industry Lobbying

Hybrid vehicles have lately been brought again into policy debates as carmakers have lobbied the European Union to weaken CO₂ targets. A planned prohibition on new internal combustion vehicles in 2035 has faced intense lobbying from the automotive industry and resistance from EU countries with large automotive manufacturing.

Some senior politicians have suggested PHEVs as a potential “compromise” solution to introduce in the regulation.

One external energy policy expert, who was not involved with the study, described the analysis a “highly valuable addition” after a long period in which segments of the car sector claimed there was too little information to properly evaluate actual emissions.

“These findings show, beyond any doubt, that the difference in lab and real-world PHEV fuel consumption and CO₂ emissions is much, much greater than for gasoline or conventional cars,” they stated. “All regulatory changes concerning PHEVs should be made with extreme care and in the light of this data.”