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Plug-in hybrid electric vehicles release almost five times greater global warming pollution than lab-reported figures indicate, according to a new analysis.

Growing Gap In Official and Actual Emissions

Data reveals that PHEVs release just one-fifth lower 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 three-quarters reduction in pollution.

Researchers examined data from in-vehicle energy use monitors of 800,000 cars sold in the EU from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, increased from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported emissions are falling,” said a lead analyst involved in the study. “This gap is widening and poses a significant issue. Consequently, PHEVs pollute nearly as much as petrol cars.”

Key Reasons Driving the Emissions Gap

Researchers attributed the majority of the difference to overestimates of the “electric driving share” – the ratio of miles travelled in electric mode compared to overall mileage. They found that just 27% of travel was done in EV mode, whereas official assumptions assumed over four-fifths.

Additionally, when operating in electric mode, pollution levels were well above lab projections. This happened because electric motors were insufficiently powerful sufficient to function independently, leading to engines burning gasoline for almost one-third of the travel completed in EV mode.

Regulatory and Financial Consequences

Based on estimates, the underestimation of PHEV emissions enabled four major automaker companies to escape over €5bn in fines from 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs could spend approximately €500 more per year in operating expenses than would be estimated under lab tests.

“The strong claims that manufacturers like to make about their PHEV cars are obviously way off the mark,” stated a automotive analyst. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are little better than standard gas and diesel vehicles in terms of energy use, CO₂ emissions, and running costs.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid vehicles have recently been brought back into policy debates as carmakers have pressed the European Union to relax CO₂ standards. A proposed ban on new combustion engine vehicles in 2035 has faced heavy pressure from the automotive industry and resistance from member states with significant car industries.

Several senior politicians have proposed PHEVs as a possible “compromise” solution to introduce in the regulation.

One independent energy economics expert, who was not involved with the study, called the analysis a “highly valuable addition” after years in which segments of the automotive industry claimed there was too little information to accurately assess real-world CO2 output.

“The results demonstrate, without question, that the difference between lab and actual PHEV fuel consumption and CO₂ output is much, much greater than for petrol or conventional cars,” the expert stated. “Any policy adjustments concerning PHEVs should be made with utmost caution and considering this evidence.”