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Plug-in hybrid electric vehicles emit almost five times more global warming pollution than lab-reported data show, according to a new report.

Growing Gap In Lab and Actual Emissions

Data reveals that PHEVs emit just one-fifth less CO₂ than conventional gas and diesel vehicles, based on analysis carried out by a non-profit group. This contrasts sharply with laboratory estimates, which assumed a three-quarters decrease in pollution.

Researchers examined information from in-vehicle energy use meters of 800,000 vehicles sold in Europe from 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, up from 3.5 times in 2021.

“Actual CO2 output are rising, while official emissions are falling,” said a senior researcher participating in the report. “That gap is growing and poses a significant issue. Consequently, PHEVs emit almost as heavily as petrol cars.”

Key Reasons Behind the Emissions Gap

Analysts linked most of the gap to overestimates of the “utility factor” – the ratio of kilometers travelled in battery power compared to overall mileage. The team found that just 27% of travel was done in electric mode, whereas official assumptions suggested 84%.

Additionally, when operating in electric mode, emission amounts were well above official estimates. This occurred because EV motors were not strong enough to function independently, leading to combustion motors using fossil fuels for nearly one-third of the distance covered in electric mode.

Policy and Economic Implications

According to calculations, the lowballing of PHEV emissions allowed four major automaker companies to escape over €5bn in penalties between 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs could pay approximately €500 extra per year in running expenses than is estimated under laboratory tests.

“The strong statements that automakers like to make about their plug-in hybrid cars are clearly way off the truth,” stated a automotive expert. “Consumers are being duped into believing that by purchasing a PHEV, they are helping the planet and cutting money. In reality, PHEVs are little improved than regular gas and diesel cars in terms of fuel consumption, CO₂ production, and running expenses.”

Political Debate and Automotive Lobbying

Plug-in hybrid cars have recently been drawn again into policy debates as automakers have pressed the European Union to weaken CO₂ targets. A planned ban on new internal combustion cars in 2035 has faced heavy lobbying from the car sector and opposition from EU countries with large car industries.

Some high-level officials have suggested PHEVs as a potential “compromise” option to include in the regulation.

An external energy economics expert, who was not involved with the study, called the analysis a “highly valuable contribution” after a long period in which segments of the automotive industry claimed there was insufficient information to accurately evaluate actual CO2 output.

“The results demonstrate, without question, that the gap between lab and actual PHEV fuel consumption and CO₂ output is much, much larger than for petrol or diesel cars,” they stated. “Any policy changes regarding PHEVs should be made with extreme caution and considering this evidence.”