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Plug-in hybrid electric vehicles release almost five times greater planet-heating pollution than official data show, according to a new analysis.

Growing Gap In Lab and Actual Emissions

Data shows that PHEVs emit just 19% lower CO₂ than conventional petrol and diesel vehicles, based on analysis carried out by a non-profit group. This contrasts significantly with lab tests, which assumed a three-quarters reduction in emissions.

Researchers examined information from in-vehicle fuel consumption meters of eight hundred thousand vehicles registered in Europe between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, increased from 3.5 times in 2021.

“Actual emissions are increasing, while lab-reported emissions are decreasing,” said a senior analyst involved in the report. “This gap is widening and poses a serious issue. As a result, PHEVs pollute nearly as heavily as petrol cars.”

Primary Factors Behind the Emissions Gap

Researchers linked the majority of the gap to inflated estimates of the “utility factor” – the percentage of miles travelled in battery mode relative to total mileage. The team determined that just 27% of travel was done in EV mode, while lab estimates assumed over four-fifths.

Even, when running in EV mode, emission amounts were well above lab estimates. That occurred because electric motors were not strong enough to operate independently, resulting to combustion motors using fossil fuels for nearly a third of the travel covered in electric mode.

Regulatory and Financial Implications

Based on estimates, the lowballing of PHEV emissions allowed several major carmaker companies to escape over €5bn in fines from 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ standards.

Furthermore, owners of PHEVs would spend approximately €500 more annually in running costs than is estimated under laboratory tests.

“The bold claims that automakers often promote about their PHEV vehicles are obviously far from the mark,” stated a automotive analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are little better than regular gas and diesel cars in terms of fuel use, CO₂ emissions, and running costs.”

Political Discussion and Automotive Lobbying

Hybrid vehicles have lately been brought again into policy debates as carmakers have pressed the European Union to weaken CO₂ standards. A planned prohibition on new internal combustion vehicles in 2035 has faced heavy pressure from the car sector and opposition from EU countries with large automotive industries.

Some senior politicians have proposed PHEVs as a possible “compromise” option to introduce in the regulation.

One independent energy policy expert, who was not involved with the study, called the report a “very useful contribution” after a long period in which parts of the automotive industry argued there was insufficient data to accurately evaluate actual emissions.

“These findings show, without question, that the difference between official and actual PHEV energy use and CO₂ emissions is much, much greater than for gasoline or diesel cars,” they stated. “Any regulatory changes regarding PHEVs should be made with extreme care and considering this evidence.”