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Plug-in hybrid electric vehicles release nearly 5x more global warming pollution than official data indicate, according to a new report.

Widening Discrepancy In Lab and Actual Emissions

Statistics shows that PHEVs release just 19% less CO₂ than traditional gas and diesel cars, according to analysis conducted by a non-profit organization. That differs sharply with laboratory estimates, which assumed a three-quarters decrease in emissions.

Analysts examined data from onboard energy use meters of 800,000 cars sold in Europe between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, increased from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported emissions are decreasing,” stated a senior researcher participating in the study. “That gap is widening and creates a serious issue. As a result, PHEVs emit almost as much as petrol vehicles.”

Primary Factors Behind the Emissions Gap

Analysts linked most of the difference to overestimates of the “electric driving share” – the percentage of miles driven in battery mode relative to overall mileage. They determined that only a quarter of driving was done in electric mode, whereas official assumptions assumed 84%.

Even, when running in electric mode, emission amounts were significantly higher than lab projections. This occurred because electric motors were insufficiently powerful enough to function alone, resulting to engines burning gasoline for nearly one-third of the distance covered in electric mode.

Regulatory and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output allowed four large carmaker groups to avoid over €5bn in fines between 2021 and 2023, by falsely easing adherence with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs could spend about €500 more annually in running costs than is estimated under lab tests.

“The bold statements that manufacturers often promote about their PHEV cars are clearly way off the truth,” commented a automotive analyst. “Buyers are being duped into believing that by buying a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are little improved than standard gas and diesel vehicles in terms of fuel use, CO₂ production, and running expenses.”

Political Discussion and Automotive Lobbying

Hybrid vehicles have lately been brought back into political discussions as carmakers have lobbied the EU to relax CO₂ targets. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the automotive industry and resistance from member states with significant car industries.

Several high-level officials have suggested plug-in hybrids as a possible “flexibility” solution to include in the regulation.

An independent energy economics expert, who was unaffiliated with the research, described the report a “very useful addition” after a long period in which parts of the car industry claimed there was insufficient data to properly evaluate actual emissions.

“The results show, beyond any doubt, that the gap in lab and real-world PHEV fuel consumption and CO₂ emissions is significantly larger than for petrol or diesel cars,” the expert stated. “Any regulatory changes concerning PHEVs should be implemented with utmost caution and in the light of this evidence.”