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Plug-in hybrid electric vehicles release nearly five times greater global warming pollution than lab-reported figures indicate, as per a new report.

Growing Gap Between Lab and Actual Emissions

Data reveals that PHEVs release just 19% less CO₂ than traditional gas and diesel vehicles, according to research conducted by a advocacy group. This contrasts sharply with lab estimates, which assumed a three-quarters decrease in pollution.

Analysts examined information from onboard fuel consumption meters of 800,000 cars sold in Europe between 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official estimates, increased from 3.5 times in 2021.

“Actual emissions are increasing, while official figures are decreasing,” stated a lead researcher participating in the study. “This gap is widening and poses a serious problem. Consequently, PHEVs emit nearly as heavily as petrol cars.”

Primary Factors Driving the Emissions Gap

Researchers attributed the majority of the gap to overestimates of the “utility factor” – the ratio of kilometers driven in battery mode relative to total mileage. The team determined that only a quarter of driving was done in electric mode, while lab estimates suggested 84%.

Additionally, when running in EV mode, emission amounts were significantly higher than lab estimates. That happened because EV motors were insufficiently powerful enough to function alone, resulting to engines burning gasoline for almost one-third of the distance covered in electric mode.

Policy and Economic Consequences

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

Additionally, drivers of PHEVs would spend about €500 more annually in running expenses than would be estimated under lab conditions.

“The bold statements that automakers like to make about their PHEV vehicles are obviously way off the mark,” commented a automotive analyst. “Buyers are being duped into thinking that by buying a PHEV, they are helping the environment and saving costs. In reality, PHEVs are only slightly improved than regular petrol and diesel cars in terms of energy consumption, CO₂ emissions, and operating costs.”

Policy Discussion and Industry Pressure

Hybrid vehicles have recently been brought again into political discussions as automakers have lobbied the EU to weaken CO₂ targets. A planned ban on new internal combustion vehicles in 2035 has faced intense lobbying from the automotive sector and opposition from EU countries with large automotive manufacturing.

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

One independent energy policy specialist, who was not involved with the study, called the analysis a “very useful addition” after years in which parts of the car sector claimed there was too little data to properly evaluate actual emissions.

“The results show, without question, that the difference in lab and actual PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or conventional cars,” the expert said. “Any regulatory adjustments concerning PHEVs should be made with extreme care and considering this data.”