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

Growing Gap In Official and Real-World Emissions

Statistics shows that PHEVs release just 19% less CO₂ than traditional petrol and diesel vehicles, according to analysis conducted by a non-profit group. That contrasts sharply with lab estimates, which suggested a three-quarters decrease in emissions.

Researchers examined information from in-vehicle energy use monitors of 800,000 cars registered in the EU between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, up from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are falling,” stated a senior analyst participating in the report. “This discrepancy is growing and poses a serious problem. Consequently, PHEVs emit nearly as heavily as gasoline cars.”

Primary Reasons Driving the Emissions Gap

Analysts linked most of the difference to overestimates of the “electric driving share” – the percentage of miles travelled in electric power relative to total mileage. They found that just a quarter of driving was completed in EV mode, whereas official estimates suggested over four-fifths.

Additionally, when operating in EV mode, emission levels were well above official projections. That occurred because EV motors were insufficiently powerful sufficient to operate independently, resulting to combustion motors burning gasoline for nearly a third of the distance completed in EV mode.

Regulatory and Financial Consequences

Based on estimates, the lowballing of PHEV emissions allowed four large automaker companies to avoid over €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs could pay about €500 more annually in running expenses than is assumed under lab tests.

“The bold statements that automakers often promote 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 helping the planet and saving money. Actually, PHEVs are only slightly improved than regular petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating expenses.”

Policy Discussion and Automotive Lobbying

Hybrid vehicles have recently been drawn again into policy discussions as carmakers have pressed the European Union to relax CO₂ standards. A planned ban on sales of new internal combustion cars in 2035 has faced heavy pressure from the automotive sector and opposition from member states with large car manufacturing.

Some high-level officials have proposed plug-in hybrids as a possible “flexibility” solution to introduce in the regulation.

One external energy economics expert, who was unaffiliated with the study, called the analysis a “very useful addition” after a long period in which parts of the car sector claimed there was insufficient data to properly evaluate real-world emissions.

“These findings show, without question, that the gap in lab and real-world PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or conventional vehicles,” the expert said. “Any policy adjustments concerning PHEVs should be made with utmost care and in the light of that evidence.”