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Plug-in hybrid electric vehicles release nearly 5x more planet-heating emissions than official data show, according to a new report.

Growing Gap In Lab and Real-World Emissions

Statistics reveals that PHEVs emit just one-fifth less CO₂ than conventional petrol and diesel vehicles, according to analysis carried out by a advocacy group. That contrasts sharply with lab tests, which assumed a 75% reduction in pollution.

Analysts examined information from in-vehicle energy use meters of 800,000 vehicles registered in the EU from 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, up from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported figures are decreasing,” said a lead analyst involved in the study. “This gap is widening and creates a significant problem. Consequently, PHEVs pollute almost as heavily as petrol cars.”

Key Factors Behind the Emissions Gap

Analysts linked most of the difference to inflated estimates of the “utility factor” – the ratio of miles travelled in electric mode compared to overall distance. The team determined that only 27% of driving was done in EV mode, whereas lab assumptions suggested 84%.

Additionally, when operating in EV mode, emission amounts were well above lab estimates. This happened because EV motors were insufficiently powerful enough to function independently, leading to engines burning fossil fuels for almost one-third of the distance completed in EV mode.

Policy and Economic Implications

According to estimates, the lowballing of PHEV emissions allowed four large carmaker groups to escape more than €5bn in penalties between 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ targets.

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

“The bold claims that automakers often promote 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 helping the environment and saving costs. Actually, PHEVs are little improved than standard gas and diesel cars in terms of fuel use, CO₂ production, and running costs.”

Political Discussion and Automotive Pressure

Hybrid cars have recently been brought again into policy debates as carmakers have pressed the EU to weaken CO₂ standards. A proposed ban on new internal combustion cars in 2035 has faced intense lobbying from the car industry and resistance from member states with large automotive manufacturing.

Several senior politicians have suggested plug-in hybrids as a potential “compromise” option to include in the regulation.

An external energy economics expert, who was not involved with the research, called the analysis a “highly valuable addition” after years in which segments of the car sector claimed there was insufficient information to properly evaluate actual emissions.

“The results demonstrate, beyond any doubt, that the difference between official and actual PHEV energy use and CO₂ emissions is much, much greater than for gasoline or diesel cars,” the expert stated. “All regulatory changes concerning PHEVs should be implemented with extreme caution and considering that data.”