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Plug-in hybrid cars emit nearly 5x more planet-heating emissions than official data show, as per a new analysis.

Growing Discrepancy In Lab and Real-World CO2 Output

Data shows that PHEVs emit only 19% less CO₂ than traditional petrol and diesel cars, according to research conducted by a advocacy organization. That differs significantly with lab tests, which assumed a three-quarters reduction in emissions.

Analysts studied data from in-vehicle energy use monitors of 800,000 vehicles registered in Europe between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab figures, up from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported emissions are falling,” stated a senior researcher participating in the report. “This discrepancy is widening and creates a serious problem. Consequently, PHEVs emit almost as much as petrol vehicles.”

Key Factors Behind the Emissions Gap

Analysts linked the majority of the gap to overestimates of the “utility factor” – the percentage of kilometers travelled in electric power compared to total mileage. They found that only 27% of driving was completed in EV mode, while lab estimates assumed 84%.

Even, when operating in EV mode, emission levels were significantly higher than lab estimates. This occurred because electric motors were not strong enough to operate alone, leading to engines burning gasoline for almost one-third of the travel completed in EV mode.

Regulatory and Financial Implications

Based on estimates, the lowballing of PHEV emissions enabled four large automaker companies to avoid more than €5bn in fines between 2021 and 2023, by artificially easing adherence with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs would pay about €500 more annually in running costs than would be estimated under lab conditions.

“The bold statements that manufacturers often promote about their plug-in hybrid cars are clearly far from the truth,” commented a transport expert. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are only slightly better than regular petrol and diesel vehicles in terms of energy use, CO₂ production, and operating costs.”

Political Discussion and Industry Lobbying

Hybrid vehicles have recently been drawn back into policy debates as carmakers have lobbied the EU to weaken CO₂ standards. A proposed ban on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the automotive sector and opposition from member states with large car industries.

Several high-level politicians have proposed plug-in hybrids as a possible “flexibility” solution to introduce in the regulation.

An independent energy economics expert, who was not involved with the study, called the analysis a “very useful addition” after a long period in which segments of the car sector claimed there was insufficient information to accurately evaluate actual emissions.

“The results show, beyond any doubt, that the difference between official and real-world PHEV energy use and CO₂ output is much, much greater than for gasoline or conventional vehicles,” the expert stated. “Any policy changes concerning PHEVs should be implemented with extreme care and considering that evidence.”