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Plug-in hybrid electric vehicles emit almost 5x more global warming pollution than lab-reported data show, as per a new report.

Growing Gap Between Official and Real-World Emissions

Statistics reveals that PHEVs release only one-fifth less CO₂ than traditional gas and diesel vehicles, according to analysis carried out by a non-profit group. This contrasts sharply with lab tests, which suggested a 75% reduction in pollution.

Researchers examined information from onboard energy use monitors of 800,000 cars sold in Europe from 2021 and 2023. They found 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.

“Actual CO2 output are rising, while lab-reported figures are falling,” stated a senior analyst involved in the study. “This gap is growing and poses a serious problem. Consequently, PHEVs pollute nearly as heavily as gasoline cars.”

Primary Factors Behind the Emissions Gap

Analysts attributed the majority of the difference to inflated estimates of the “electric driving share” – the ratio of miles driven in battery mode relative to overall mileage. The team determined that just a quarter of driving was done in electric mode, whereas lab assumptions assumed 84%.

Additionally, when running in EV mode, pollution amounts were well above official estimates. That happened because electric motors were insufficiently powerful sufficient to operate alone, resulting to combustion motors using gasoline for nearly a third of the distance completed in electric mode.

Regulatory and Economic Consequences

Based on estimates, the lowballing of PHEV CO2 output enabled several large carmaker groups to escape more than €5bn in fines from 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ targets.

Additionally, owners of PHEVs would pay approximately €500 more annually in operating expenses than would be assumed under laboratory conditions.

“The strong claims that automakers often promote about their PHEV vehicles are obviously far from the truth,” commented a transport expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are only slightly better than standard petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and running expenses.”

Policy Debate and Industry Pressure

Plug-in hybrid cars have lately been drawn back into policy discussions as carmakers have lobbied the EU to relax CO₂ targets. A proposed ban on new combustion engine vehicles in 2035 has faced intense pressure from the car sector and opposition from member states with large car manufacturing.

Some senior officials have suggested plug-in hybrids as a possible “compromise” solution to include in the regulation.

One external energy economics expert, who was unaffiliated with the study, called the analysis a “very useful addition” after years in which parts of the automotive sector claimed there was too little information to accurately assess real-world CO2 output.

“These findings show, without question, that the difference between official and real-world PHEV fuel consumption and CO₂ output is significantly greater than for petrol or conventional vehicles,” they stated. “Any regulatory adjustments concerning PHEVs should be implemented with utmost care and considering that data.”