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Plug-in hybrid electric vehicles emit almost 5x more planet-heating pollution than official figures show, according to a new report.

Growing Discrepancy Between Official and Real-World CO2 Output

Data shows that PHEVs release only one-fifth lower CO₂ than conventional gas and diesel cars, according to analysis conducted by a non-profit organization. This contrasts significantly with laboratory tests, which assumed a 75% decrease in pollution.

Researchers examined information from onboard energy use meters of 800,000 vehicles registered in Europe from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official estimates, increased from three and a half times in 2021.

“Real-world emissions are rising, while official figures are falling,” stated a senior analyst involved in the study. “That discrepancy is growing and poses a significant issue. As a result, PHEVs pollute nearly as heavily as petrol cars.”

Primary Reasons Behind the Emissions Gap

Researchers linked most of the difference to overestimates of the “electric driving share” – the ratio of kilometers travelled in electric mode relative to overall distance. The team found that only a quarter of travel was done in EV mode, whereas lab assumptions assumed over four-fifths.

Even, when operating in electric mode, pollution levels were significantly higher than lab estimates. That happened because electric motors were insufficiently powerful sufficient to function independently, leading to combustion motors burning fossil fuels for almost a third of the travel completed in EV mode.

Policy and Financial Implications

According to estimates, the lowballing of PHEV emissions enabled several major automaker groups to escape over €5bn in fines from 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ standards.

Furthermore, drivers of PHEVs could pay about €500 extra annually in operating expenses than is estimated under lab conditions.

“The strong statements that manufacturers often promote about their plug-in hybrid vehicles are obviously far from the truth,” commented a transport analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and cutting costs. In reality, PHEVs are little better than standard petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and operating costs.”

Political Debate and Automotive Lobbying

Hybrid cars have recently been drawn back into policy discussions as automakers have pressed the EU to relax CO₂ standards. A planned prohibition on new combustion engine cars in 2035 has faced intense lobbying from the car sector and resistance from member states with significant automotive manufacturing.

Some high-level officials have proposed plug-in hybrids as a potential “compromise” solution to introduce in the regulation.

One external energy economics specialist, who was unaffiliated with the research, described the report a “highly valuable contribution” after a long period in which segments of the automotive industry claimed there was insufficient data to accurately evaluate actual CO2 output.

“These findings demonstrate, without question, that the gap in lab and real-world PHEV energy use and CO₂ output is significantly greater than for petrol or diesel vehicles,” they stated. “All regulatory changes concerning PHEVs should be implemented with extreme caution and considering that evidence.”