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Plug-in hybrid electric vehicles release nearly 5x greater planet-heating emissions than lab-reported data show, according to a recent report.

Widening Gap Between Official and Actual Emissions

Statistics shows that PHEVs release just 19% less CO₂ than traditional gas and diesel vehicles, based on analysis conducted by a advocacy group. This contrasts sharply with lab estimates, which assumed a 75% decrease in emissions.

Analysts examined data from in-vehicle energy use monitors of eight hundred thousand vehicles sold in Europe from 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from 3.5 times in 2021.

“Real-world emissions are rising, while official emissions are falling,” stated a lead analyst participating in the report. “That discrepancy is growing and creates a significant issue. Consequently, PHEVs emit nearly as much as gasoline cars.”

Primary Factors Driving the Emissions Gap

Researchers attributed the majority of the difference to overestimates of the “utility factor” – the ratio of kilometers travelled in electric power relative to total mileage. They found that only 27% of travel was done in EV mode, whereas official assumptions suggested over four-fifths.

Additionally, when running in EV mode, pollution levels were significantly higher than lab estimates. That happened because electric motors were not strong sufficient to function alone, leading to engines burning fossil fuels for almost a third of the travel covered in EV mode.

Policy and Economic Consequences

Based on calculations, the lowballing of PHEV emissions allowed four major automaker groups to escape more than €5bn in fines between 2021 and 2023, by falsely easing compliance with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could pay about €500 extra annually in operating costs than is assumed under lab tests.

“The bold claims that manufacturers often promote about their PHEV vehicles are obviously far from the truth,” stated a automotive analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are helping the planet and cutting money. Actually, PHEVs are little improved than standard petrol and diesel cars in terms of fuel use, CO₂ production, and running costs.”

Policy Discussion and Automotive Pressure

Plug-in hybrid cars have lately been brought back into political discussions as automakers have pressed the European Union to weaken CO₂ targets. A proposed ban on sales of new internal combustion cars in 2035 has faced intense lobbying from the automotive sector and resistance from EU countries with significant automotive industries.

Several high-level officials have proposed plug-in hybrids as a potential “compromise” option to include in the regulation.

An external energy policy expert, who was unaffiliated with the study, described the report a “very useful contribution” after a long period in which segments of the car industry argued there was too little data to accurately evaluate real-world emissions.

“The results demonstrate, without question, that the gap in official and real-world PHEV fuel consumption and CO₂ output is much, much larger than for petrol or diesel cars,” the expert stated. “Any regulatory changes concerning PHEVs should be made with utmost care and in the light of that data.”