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Plug-in hybrid cars emit nearly 5x greater planet-heating pollution than lab-reported figures indicate, according to a recent analysis.

Widening Gap In Lab and Actual CO2 Output

Statistics shows that PHEVs emit only 19% lower CO₂ than conventional gas and diesel vehicles, according to research conducted by a non-profit group. That differs significantly with lab estimates, which suggested a three-quarters decrease in emissions.

Researchers studied information from onboard energy use meters of 800,000 vehicles sold in the EU from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, up from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported figures are decreasing,” said a lead analyst participating in the study. “That gap is growing and creates a serious problem. As a result, PHEVs emit almost as heavily as gasoline vehicles.”

Key Reasons Driving the Emissions Gap

Researchers attributed most of the difference to inflated estimates of the “utility factor” – the ratio of miles driven in battery mode relative to overall mileage. They determined that just 27% of travel was done in EV mode, while official estimates suggested 84%.

Even, when operating in EV mode, emission amounts were significantly higher than lab estimates. This happened because electric motors were insufficiently powerful sufficient to function alone, leading to combustion motors burning gasoline for almost a third of the distance covered in electric mode.

Policy and Financial Consequences

According to estimates, the underestimation of PHEV emissions allowed several large carmaker groups to avoid more than €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ standards.

Furthermore, drivers of PHEVs could pay about €500 extra per year in operating expenses than would be assumed under laboratory tests.

“The bold claims that automakers like to make about their plug-in hybrid vehicles are clearly way off the mark,” stated a automotive analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are little better than standard petrol and diesel vehicles in terms of energy use, CO₂ production, and running costs.”

Policy Discussion and Industry Lobbying

Hybrid cars have lately been drawn back into policy debates as automakers have lobbied the EU to weaken CO₂ targets. A planned ban on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the car industry and resistance from EU countries with large car manufacturing.

Several senior politicians have suggested plug-in hybrids as a potential “flexibility” solution to include in the regulation.

An external energy economics expert, who was unaffiliated with the study, called the report a “highly valuable contribution” after years in which parts of the car sector claimed there was insufficient information to properly assess real-world emissions.

“The results show, without question, that the gap between official and actual PHEV energy use and CO₂ emissions is significantly greater than for petrol or diesel vehicles,” the expert said. “Any regulatory changes concerning PHEVs should be made with extreme caution and considering that data.”