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PHEVs release nearly 5x more planet-heating emissions than official data show, according to a new analysis.

Growing Gap Between Official and Actual CO2 Output

Data shows that PHEVs release only one-fifth less CO₂ than traditional gas and diesel cars, based on analysis carried out by a non-profit organization. That contrasts sharply with lab estimates, which suggested a 75% reduction in emissions.

Researchers examined data from in-vehicle fuel consumption meters of 800,000 vehicles registered in Europe between 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are decreasing,” said a senior researcher participating in the study. “This gap is growing and creates a serious problem. Consequently, PHEVs emit nearly as heavily as gasoline cars.”

Key Factors Driving the Discrepancy

Researchers attributed most of the gap to overestimates of the “electric driving share” – the ratio of miles driven in battery power relative to total mileage. They found that just a quarter of travel was done in EV mode, while lab estimates assumed 84%.

Even, when operating in electric mode, emission amounts were significantly higher than lab projections. This happened because EV motors were not strong sufficient to function alone, resulting to engines burning fossil fuels for almost a third of the distance completed in EV mode.

Policy and Economic Consequences

Based on estimates, the lowballing of PHEV CO2 output allowed several major automaker groups to escape over €5bn in penalties from 2021 and 2023, by falsely easing adherence with EU fleet-average CO₂ targets.

Additionally, drivers of PHEVs would pay approximately €500 more per year in operating expenses than is assumed under lab tests.

“The bold claims that manufacturers often promote about their plug-in hybrid cars are obviously far from the mark,” stated a automotive analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are helping the planet and saving costs. Actually, PHEVs are only slightly better than standard petrol and diesel cars in terms of energy use, CO₂ emissions, and running expenses.”

Policy Debate and Industry Pressure

Hybrid vehicles have recently been drawn back into political debates as automakers have pressed the EU to weaken CO₂ targets. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the car industry and resistance from member states with significant car manufacturing.

Several senior politicians 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 research, described the analysis a “very useful contribution” after a long period in which parts of the car sector claimed there was too little information to properly assess actual CO2 output.

“These findings demonstrate, without question, that the difference between official and real-world PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or diesel vehicles,” the expert said. “Any policy changes concerning PHEVs should be made with extreme caution and in the light of that evidence.”