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Plug-in hybrid electric vehicles release almost five times greater planet-heating pollution than lab-reported figures show, according to a new report.

Widening Discrepancy In Official and Real-World Emissions

Data reveals that PHEVs emit just one-fifth less CO₂ than traditional petrol and diesel vehicles, according to research conducted by a advocacy group. This contrasts sharply with laboratory tests, which assumed a 75% reduction in pollution.

Researchers examined data from onboard fuel consumption monitors of eight hundred thousand vehicles registered in Europe from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were nearly five times higher than official figures, up from three and a half times in 2021.

“Real-world emissions are increasing, while official figures are decreasing,” stated a senior analyst involved in the study. “That gap is widening and poses a serious problem. Consequently, PHEVs emit nearly as heavily as petrol vehicles.”

Primary Factors Driving the Discrepancy

Analysts attributed the majority of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in battery power compared to overall mileage. The team determined that just 27% of driving was completed in electric mode, while official estimates suggested 84%.

Even, when operating in EV mode, pollution amounts were well above official projections. That happened because electric motors were not strong enough to operate alone, leading to engines burning fossil fuels for nearly a third of the travel completed in EV mode.

Policy and Financial Implications

Based on calculations, the lowballing of PHEV CO2 output enabled several large automaker companies to avoid over €5bn in penalties between 2021 and 2023, by artificially easing adherence with EU average fleet CO₂ standards.

Additionally, drivers of PHEVs could spend about €500 extra annually in running costs than is estimated under lab tests.

“The strong statements that manufacturers like to make about their plug-in hybrid vehicles are obviously way off the truth,” commented a transport expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are only slightly improved than standard gas and diesel cars in terms of fuel consumption, CO₂ production, and running costs.”

Political Discussion and Industry Pressure

Plug-in hybrid vehicles have recently been drawn back into political debates as carmakers have lobbied the European Union to weaken CO₂ targets. A planned prohibition on sales of new combustion engine cars in 2035 has faced intense lobbying from the car sector and opposition from EU countries with significant automotive manufacturing.

Some senior officials have proposed PHEVs as a possible “compromise” option to include in the legislation.

An independent energy economics expert, who was not involved with the study, called the report a “very useful addition” after years in which parts of the automotive industry argued there was too little data to properly assess real-world CO2 output.

“The results show, beyond any doubt, that the gap in lab and actual PHEV fuel consumption and CO₂ output is significantly larger than for petrol or diesel vehicles,” they stated. “All policy changes regarding PHEVs should be made with utmost care and considering that evidence.”