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Plug-in hybrid electric vehicles produce nearly five times more planet-heating pollution than lab-reported figures show, as per a new report.

Widening Discrepancy In Lab and Real-World CO2 Output

Statistics shows that PHEVs emit just 19% less CO₂ than traditional petrol and diesel cars, based on research carried out by a advocacy group. This differs sharply with laboratory estimates, which assumed a 75% decrease in emissions.

Researchers studied data from in-vehicle energy use monitors of 800,000 vehicles sold in the EU between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than official figures, up from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported figures are falling,” stated a senior researcher participating in the report. “That gap is widening and poses a significant problem. Consequently, PHEVs emit almost as much as petrol vehicles.”

Primary Factors Driving the Emissions Gap

Researchers attributed the majority of the difference to inflated estimates of the “electric driving share” – the percentage of miles travelled in electric power compared to overall distance. The team found that only a quarter of travel was completed in electric mode, whereas official assumptions assumed 84%.

Even, when running in electric mode, pollution levels were well above lab projections. That occurred because EV motors were not strong enough to function alone, leading to combustion motors using fossil fuels for nearly one-third of the distance completed in electric mode.

Regulatory and Financial Implications

Based on estimates, the underestimation of PHEV CO2 output enabled four major automaker companies to avoid more than €5bn in penalties between 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs would spend approximately €500 more annually in operating costs than would be estimated under laboratory conditions.

“The bold statements that manufacturers like to make about their plug-in hybrid vehicles are obviously far from the mark,” commented a transport expert. “Buyers are being misled into believing that by buying a PHEV, they are helping the environment and cutting costs. In reality, PHEVs are little improved than standard gas and diesel vehicles in terms of fuel use, CO₂ production, and operating expenses.”

Policy Discussion and Industry Pressure

Hybrid vehicles have lately been brought again into policy discussions as carmakers have lobbied the EU to relax CO₂ targets. A planned prohibition on new combustion engine vehicles in 2035 has faced heavy lobbying from the car industry and resistance from member states with significant automotive manufacturing.

Several high-level officials have proposed plug-in hybrids as a potential “flexibility” solution to introduce in the legislation.

One external energy policy specialist, who was unaffiliated with the study, described the analysis a “highly valuable contribution” after a long period in which parts of the automotive industry claimed there was too little data to properly assess actual emissions.

“The results demonstrate, beyond any doubt, that the difference between lab and real-world PHEV fuel consumption and CO₂ output is significantly greater than for petrol or diesel cars,” the expert said. “All regulatory changes concerning PHEVs should be implemented with extreme care and considering that data.”