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Plug-in hybrid electric vehicles produce nearly five times greater planet-heating emissions than lab-reported figures indicate, according to a new report.

Widening Gap Between Official and Actual Emissions

Data shows that PHEVs release only 19% less CO₂ than conventional gas and diesel vehicles, based on analysis conducted by a advocacy organization. This contrasts significantly with lab estimates, which suggested a three-quarters decrease in emissions.

Researchers examined data from onboard energy use monitors of eight hundred thousand cars registered in the EU between 2021 and 2023. The team discovered 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.

“Real-world CO2 output are rising, while official figures are decreasing,” said a senior researcher participating in the report. “That discrepancy is growing and poses a serious issue. As a result, PHEVs emit nearly as much as petrol cars.”

Primary Factors Behind the Emissions Gap

Analysts linked the majority of the difference to overestimates of the “utility factor” – the ratio of miles travelled in battery power relative to total distance. They determined that only 27% of travel was done in EV mode, while official assumptions assumed over four-fifths.

Additionally, when running in electric mode, emission amounts were well above official estimates. That happened because EV motors were not strong sufficient to operate alone, resulting to combustion motors using fossil fuels for almost a third of the travel covered in EV mode.

Policy and Economic Implications

According to calculations, the lowballing of PHEV CO2 output enabled four large carmaker companies to avoid more than €5bn in penalties from 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs could pay about €500 more annually in running costs than would be estimated under laboratory tests.

“The bold claims that automakers often promote about their plug-in hybrid cars are clearly far from the truth,” commented a automotive analyst. “Consumers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are little improved than standard gas and diesel vehicles in terms of fuel consumption, CO₂ production, and operating expenses.”

Policy Discussion and Industry Pressure

Plug-in hybrid vehicles have lately been brought again into political discussions as automakers have pressed the European Union to relax CO₂ standards. A planned ban on new internal combustion cars in 2035 has faced intense lobbying from the car industry and resistance from EU countries with significant automotive industries.

Some high-level officials have proposed PHEVs as a potential “compromise” option to include in the regulation.

One external energy economics expert, who was not involved with the study, called the analysis a “very useful contribution” after a long period in which segments of the car industry claimed there was too little data to accurately evaluate actual emissions.

“These findings demonstrate, beyond any doubt, that the difference in lab and real-world PHEV energy use and CO₂ output is significantly greater than for gasoline or conventional vehicles,” the expert said. “All policy adjustments concerning PHEVs should be made with utmost care and considering that evidence.”