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PHEVs release nearly 5x greater planet-heating pollution than lab-reported data show, according to a new report.

Widening Discrepancy Between Lab and Actual CO2 Output

Data reveals that PHEVs emit only 19% less CO₂ than conventional petrol and diesel vehicles, based on analysis conducted by a non-profit group. That contrasts significantly with laboratory tests, which assumed a three-quarters decrease in pollution.

Researchers studied information from onboard energy use monitors of eight hundred thousand cars registered in the EU from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab estimates, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are falling,” said a lead researcher involved in the report. “This gap is widening and poses a serious issue. Consequently, PHEVs pollute nearly as heavily as gasoline vehicles.”

Key Factors Driving the Discrepancy

Researchers linked the majority of the gap to inflated estimates of the “utility factor” – the percentage of miles driven in battery power compared to overall distance. They determined that only a quarter of driving was done in electric mode, whereas lab assumptions assumed 84%.

Additionally, when operating in electric mode, emission amounts were significantly higher than lab projections. That happened because EV motors were insufficiently powerful sufficient to function alone, resulting to combustion motors burning fossil fuels for nearly one-third of the distance covered in electric mode.

Policy and Economic Consequences

According to estimates, the lowballing of PHEV CO2 output allowed several major carmaker companies to avoid more than €5bn in fines between 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ standards.

Furthermore, drivers of PHEVs would spend about €500 extra annually in running expenses than would be assumed under lab tests.

“The bold claims that manufacturers like to make about their PHEV vehicles are clearly way off the mark,” stated a automotive analyst. “Buyers are being misled into thinking that by buying a PHEV, they are helping the environment and cutting money. In reality, PHEVs are little better than standard gas and diesel cars in terms of fuel consumption, CO₂ emissions, and operating costs.”

Policy Discussion and Industry Lobbying

Plug-in hybrid cars have lately been brought back into policy debates as automakers have pressed the EU to relax CO₂ standards. A planned ban on new combustion engine cars in 2035 has faced intense pressure from the automotive sector and resistance from EU countries with large car industries.

Some senior politicians have suggested PHEVs as a potential “compromise” solution to introduce in the legislation.

One independent energy policy expert, who was not involved with the study, called the report a “highly valuable addition” after years in which parts of the car industry argued there was insufficient information to properly assess real-world CO2 output.

“These findings demonstrate, without question, that the difference in official and actual PHEV fuel consumption and CO₂ emissions is significantly greater than for petrol or conventional cars,” they said. “All regulatory changes concerning PHEVs should be made with utmost care and in the light of that data.”