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PHEVs emit almost 5x more planet-heating pollution than lab-reported data show, according to a new analysis.

Growing Gap Between Lab and Actual Emissions

Data shows that PHEVs emit just one-fifth lower CO₂ than conventional gas and diesel vehicles, according to analysis conducted by a advocacy organization. That differs significantly with laboratory estimates, which assumed a 75% reduction in emissions.

Analysts studied information from in-vehicle energy use meters of 800,000 vehicles sold in Europe between 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, increased from three and a half times in 2021.

“Actual emissions are rising, while lab-reported figures are decreasing,” said a lead researcher participating in the report. “This discrepancy is growing and creates a serious problem. As a result, PHEVs pollute almost as heavily as gasoline cars.”

Key Factors Driving the Discrepancy

Analysts linked most of the gap to overestimates of the “electric driving share” – the ratio of miles driven in battery power relative to overall mileage. They determined that only a quarter of driving was completed in EV mode, while official assumptions assumed 84%.

Even, when operating in EV mode, emission amounts were well above lab projections. That occurred because electric motors were not strong enough to operate alone, resulting to engines burning gasoline for nearly one-third of the travel completed in electric mode.

Policy and Economic Consequences

According to estimates, the lowballing of PHEV CO2 output enabled four major automaker companies to avoid more than €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs could pay about €500 more per year in operating expenses than would be assumed under lab tests.

“The bold claims that manufacturers like to make about their plug-in hybrid vehicles are clearly way off the truth,” stated a automotive analyst. “Consumers are being duped into believing that by buying a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are little better than standard petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and operating expenses.”

Political Debate and Industry Lobbying

Plug-in hybrid vehicles have recently been drawn again into political discussions as automakers have pressed the EU to relax CO₂ standards. A proposed prohibition on new internal combustion cars in 2035 has faced heavy pressure from the automotive sector and resistance from member states with significant car manufacturing.

Some high-level officials have suggested plug-in hybrids as a potential “compromise” solution to include in the regulation.

An independent energy policy expert, who was unaffiliated with the research, described the analysis a “very useful contribution” after years in which segments of the automotive sector claimed there was too little information to properly assess actual CO2 output.

“These findings show, without question, that the difference in lab and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or diesel cars,” they said. “All regulatory changes concerning PHEVs should be implemented with extreme care and in the light of that data.”