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PHEVs emit nearly five times more global warming pollution than official figures indicate, according to a new report.

Widening Discrepancy Between Lab and Real-World CO2 Output

Statistics reveals that PHEVs emit just one-fifth less CO₂ than traditional petrol and diesel vehicles, according to research conducted by a non-profit group. That contrasts sharply with lab estimates, which suggested a three-quarters decrease in pollution.

Analysts examined data from onboard fuel consumption meters of 800,000 cars registered in Europe between 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were nearly five times greater than lab figures, increased from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported figures are decreasing,” stated a lead researcher participating in the report. “That discrepancy is growing and creates a serious problem. Consequently, PHEVs emit almost as heavily as petrol cars.”

Primary Reasons Driving the Discrepancy

Researchers linked the majority of the difference to overestimates of the “utility factor” – the percentage of miles travelled in electric mode relative to total mileage. They determined that just 27% of travel was completed in electric mode, while lab estimates suggested over four-fifths.

Even, when operating in electric mode, pollution amounts were significantly higher than lab projections. This happened because EV motors were not strong enough to operate alone, leading to engines using fossil fuels for almost a third of the travel completed in electric mode.

Regulatory and Economic Consequences

Based on estimates, the underestimation of PHEV emissions enabled several major carmaker groups to avoid over €5bn in fines between 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ standards.

Additionally, drivers of PHEVs could spend approximately €500 more per year in running costs than would be estimated under lab tests.

“The bold statements that manufacturers like to make about their plug-in hybrid cars are clearly way off the mark,” commented a automotive expert. “Consumers are being misled into thinking that by buying a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are only slightly improved than regular gas and diesel cars in terms of energy use, CO₂ production, and operating expenses.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid cars have lately been brought back into policy debates as automakers have lobbied the European Union to weaken CO₂ standards. A planned prohibition on sales of new internal combustion cars in 2035 has faced intense lobbying from the automotive industry and opposition from member states with significant car manufacturing.

Some senior officials have suggested plug-in hybrids as a potential “compromise” option to introduce in the legislation.

One external energy policy specialist, who was not involved with the study, called the report a “highly valuable contribution” after a long period in which segments of the automotive sector claimed there was insufficient information to accurately assess actual CO2 output.

“The results show, beyond any doubt, that the gap between lab and real-world PHEV fuel consumption and CO₂ emissions is much, much greater than for gasoline or conventional vehicles,” they said. “Any regulatory adjustments regarding PHEVs should be implemented with extreme caution and in the light of that data.”