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Plug-in hybrid electric vehicles emit nearly 5x more planet-heating pollution than lab-reported data show, as per a recent report.

Growing Discrepancy In Lab and Real-World Emissions

Data reveals that PHEVs emit just one-fifth less CO₂ than conventional petrol and diesel cars, according to research carried out by a non-profit organization. That differs sharply with laboratory estimates, which assumed a three-quarters reduction in pollution.

Researchers examined data from onboard energy use meters of eight hundred thousand vehicles registered in Europe from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, increased from three and a half times in 2021.

“Real-world emissions are increasing, while official figures are falling,” stated a senior researcher participating in the study. “This gap is growing and poses a serious issue. As a result, PHEVs pollute almost as much as petrol cars.”

Key Factors Behind the Emissions Gap

Researchers attributed most of the difference to inflated estimates of the “utility factor” – the percentage of kilometers driven in battery power compared to overall mileage. The team found that just 27% of driving was completed in EV mode, while official assumptions assumed 84%.

Additionally, when operating in electric mode, emission levels were well above lab projections. That happened because electric motors were insufficiently powerful sufficient to operate alone, resulting to engines burning gasoline for almost one-third of the travel covered in electric mode.

Policy and Economic Consequences

Based on estimates, the underestimation of PHEV emissions allowed four major carmaker companies to escape more than €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ standards.

Furthermore, drivers of PHEVs would spend approximately €500 more annually in running expenses than would be assumed under laboratory tests.

“The strong statements that automakers like to make about their PHEV cars are obviously far from the mark,” commented a transport analyst. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are only slightly better than regular petrol and diesel vehicles in terms of energy use, CO₂ production, and operating costs.”

Policy Debate and Automotive Pressure

Plug-in hybrid cars have lately been drawn again into political debates as carmakers have pressed the EU to relax CO₂ standards. A proposed ban on sales of new internal combustion vehicles in 2035 has faced intense pressure from the car industry and resistance from member states with significant automotive industries.

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

One external energy policy specialist, who was unaffiliated with the research, called the analysis a “highly valuable contribution” after a long period in which parts of the automotive industry claimed there was insufficient data to properly assess real-world CO2 output.

“These findings show, without question, that the gap between lab and actual PHEV fuel consumption and CO₂ output is significantly greater than for petrol or diesel cars,” the expert stated. “Any policy changes regarding PHEVs should be made with extreme caution and considering that evidence.”