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Plug-in hybrid cars produce nearly five times greater global warming pollution than official data show, according to a recent report.

Growing Gap Between Official and Real-World Emissions

Data shows that PHEVs emit only one-fifth less CO₂ than traditional petrol and diesel vehicles, according to research carried out by a advocacy organization. This contrasts sharply with laboratory tests, which suggested a three-quarters reduction in pollution.

Researchers examined information from onboard energy use meters of 800,000 vehicles sold in the EU between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are falling,” said a lead researcher participating in the report. “This gap is growing and creates a serious issue. As a result, PHEVs pollute nearly as much as gasoline cars.”

Primary Factors Behind the Discrepancy

Analysts attributed most of the difference to overestimates of the “utility factor” – the ratio of kilometers travelled in battery power compared to overall distance. They determined that just a quarter of driving was done in electric mode, whereas lab estimates suggested over four-fifths.

Additionally, when operating in EV mode, pollution levels were well above official estimates. That happened because electric motors were insufficiently powerful sufficient to operate independently, leading to engines burning gasoline for nearly a third of the distance completed in EV mode.

Regulatory and Financial Implications

According to estimates, the underestimation of PHEV emissions enabled several large carmaker companies to escape over €5bn in fines from 2021 and 2023, by falsely easing compliance with European Union fleet-average CO₂ targets.

Additionally, owners of PHEVs could spend approximately €500 more annually in operating costs than is estimated under laboratory conditions.

“The strong claims that manufacturers often promote about their plug-in hybrid cars are clearly way off the mark,” commented a automotive analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are only slightly better than standard gas and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating costs.”

Political Discussion and Industry Lobbying

Plug-in hybrid vehicles have lately been drawn back into policy debates as carmakers have pressed the EU to relax CO₂ standards. A planned ban on new internal combustion cars in 2035 has faced intense lobbying from the automotive sector and resistance from member states with large car industries.

Several senior officials have suggested PHEVs as a potential “compromise” solution to introduce in the legislation.

One external energy policy expert, who was not involved with the study, called the report a “highly valuable addition” after a long period in which segments of the automotive industry argued there was insufficient data to accurately evaluate actual CO2 output.

“The results demonstrate, without question, that the difference in official and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or diesel cars,” they said. “All regulatory changes regarding PHEVs should be made with utmost care and considering that data.”