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Plug-in hybrid electric vehicles emit almost five times greater global warming emissions than official figures indicate, according to a new analysis.

Growing Gap Between Lab and Actual CO2 Output

Data shows that PHEVs release only one-fifth less CO₂ than traditional gas and diesel cars, according to research carried out by a advocacy organization. That contrasts significantly with lab estimates, which suggested a 75% reduction in pollution.

Analysts studied data from in-vehicle fuel consumption meters of eight hundred thousand cars sold in Europe between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, up from three and a half times in 2021.

“Real-world emissions are increasing, while official figures are decreasing,” stated a senior researcher involved in the report. “This discrepancy is growing and poses a significant problem. Consequently, PHEVs emit almost as heavily as gasoline cars.”

Primary Factors Behind the Emissions Gap

Researchers linked the majority of the difference to inflated estimates of the “utility factor” – the percentage of kilometers driven in battery power relative to overall distance. They found that only 27% of driving was completed in electric mode, while lab estimates suggested over four-fifths.

Additionally, when operating in EV mode, pollution levels were significantly higher than lab projections. That happened because EV motors were insufficiently powerful enough to function independently, resulting to engines using fossil fuels for almost one-third of the travel completed in EV mode.

Regulatory and Economic Consequences

Based on estimates, the lowballing of PHEV CO2 output enabled four large carmaker companies to escape over €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs would spend about €500 more annually in operating expenses than would be assumed under laboratory conditions.

“The strong statements that manufacturers often promote about their plug-in hybrid cars are clearly far from the truth,” commented a transport analyst. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are little improved than standard gas and diesel cars in terms of fuel use, CO₂ emissions, and running expenses.”

Policy Debate and Industry Pressure

Hybrid vehicles have recently been drawn back into policy debates as automakers have pressed the EU to relax CO₂ targets. A planned prohibition on sales of new internal combustion cars in 2035 has faced intense pressure from the car sector and resistance from member states with significant automotive industries.

Several senior politicians have proposed plug-in hybrids as a possible “flexibility” solution to introduce in the regulation.

One external energy policy specialist, who was unaffiliated with the research, described the report a “highly valuable addition” after a long period in which segments of the car sector claimed there was too little data to properly evaluate actual emissions.

“These findings demonstrate, beyond any doubt, that the difference in lab and real-world PHEV fuel consumption and CO₂ emissions is much, much greater than for gasoline or conventional vehicles,” the expert said. “Any policy adjustments concerning PHEVs should be implemented with utmost caution and considering that data.”