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PHEVs emit almost 5x more global warming pollution than official data indicate, according to a new report.

Growing Discrepancy Between Official and Real-World Emissions

Statistics reveals that PHEVs release just one-fifth lower CO₂ than conventional gas and diesel vehicles, according to analysis conducted by a advocacy group. That contrasts sharply with laboratory tests, which suggested a 75% reduction in emissions.

Analysts examined information from onboard fuel consumption monitors of 800,000 vehicles registered in Europe between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are falling,” stated a senior researcher participating in the report. “This gap is widening and poses a significant issue. As a result, PHEVs pollute almost as heavily as gasoline cars.”

Primary Reasons Driving the Discrepancy

Researchers attributed most of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in electric power relative to total mileage. The team found that just a quarter of driving was completed in electric mode, while lab estimates suggested over four-fifths.

Even, when operating in EV mode, emission levels were significantly higher than lab projections. This happened because electric motors were not strong enough to function independently, leading to combustion motors using fossil fuels for nearly one-third of the distance completed in EV mode.

Policy and Economic Implications

Based on estimates, the underestimation of PHEV emissions allowed four large automaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ standards.

Additionally, owners of PHEVs would spend about €500 extra annually in running costs than would be estimated under lab tests.

“The bold statements that automakers often promote about their PHEV cars are obviously way off the mark,” commented a transport expert. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are only slightly improved than standard gas and diesel cars in terms of fuel consumption, CO₂ production, and running costs.”

Policy Discussion and Industry Pressure

Plug-in hybrid cars have lately been drawn again into political discussions as automakers have pressed the European Union to weaken CO₂ standards. A proposed prohibition on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the car industry and opposition from EU countries with significant car industries.

Several high-level politicians have suggested plug-in hybrids as a possible “flexibility” solution to include in the legislation.

An external energy economics expert, who was not involved with the study, described the analysis a “highly valuable addition” after years in which segments of the car sector claimed there was too little data to accurately evaluate actual CO2 output.

“The results show, beyond any doubt, that the difference between lab and real-world PHEV energy use and CO₂ emissions is much, much larger than for petrol or conventional vehicles,” they stated. “All regulatory adjustments regarding PHEVs should be made with utmost caution and in the light of that data.”