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PHEVs emit nearly 5x more planet-heating emissions than official figures show, according to a new analysis.

Growing Gap In Lab and Real-World Emissions

Data reveals that PHEVs emit just 19% less CO₂ than conventional gas and diesel cars, according to analysis conducted by a non-profit group. That differs significantly with laboratory tests, which assumed a 75% reduction in pollution.

Analysts studied data from onboard fuel consumption meters of 800,000 vehicles registered in the EU between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than official figures, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are decreasing,” said a senior researcher participating in the study. “That discrepancy is growing and creates a significant problem. As a result, PHEVs pollute almost as heavily as petrol vehicles.”

Key Factors Driving the Emissions Gap

Analysts attributed most of the gap to inflated estimates of the “electric driving share” – the ratio of miles driven in electric mode relative to overall mileage. They determined that only 27% of driving was completed in electric mode, whereas lab assumptions suggested 84%.

Even, when running in electric mode, emission amounts were well above official estimates. That happened because EV motors were not strong enough to operate alone, leading to combustion motors burning fossil fuels for nearly one-third of the distance completed in EV mode.

Regulatory and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output enabled four large carmaker companies to avoid more than €5bn in fines from 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs would spend about €500 more annually in running costs than is estimated under laboratory conditions.

“The strong claims that manufacturers like to make about their PHEV cars are clearly far from the mark,” commented a automotive analyst. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of fuel use, CO₂ production, and operating expenses.”

Political Discussion and Automotive Lobbying

Plug-in hybrid cars have lately been drawn again into policy discussions as automakers have pressed the EU to relax CO₂ standards. A planned ban on new internal combustion vehicles in 2035 has faced intense lobbying from the automotive industry and resistance from EU countries with large automotive manufacturing.

Several high-level politicians have proposed PHEVs as a potential “flexibility” option to include in the regulation.

An external energy economics expert, who was unaffiliated with the study, called the report a “highly valuable contribution” after years in which segments of the car industry argued there was insufficient data to accurately evaluate actual CO2 output.

“The results demonstrate, beyond any doubt, that the gap in lab and actual PHEV energy use and CO₂ output is significantly greater than for petrol or conventional vehicles,” the expert stated. “All regulatory adjustments regarding PHEVs should be implemented with utmost care and considering this evidence.”