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Plug-in hybrid electric vehicles release nearly 5x greater global warming pollution than lab-reported data show, according to a recent report.

Widening Gap Between Official and Actual Emissions

Statistics shows that PHEVs emit only 19% lower CO₂ than traditional gas and diesel vehicles, based on research conducted by a advocacy organization. This differs significantly with lab tests, which suggested a 75% decrease in emissions.

Analysts studied data from onboard energy use meters of eight hundred thousand cars sold in the EU from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official estimates, increased from three and a half times in 2021.

“Actual emissions are rising, while official emissions are falling,” stated a lead researcher involved in the study. “This discrepancy is widening and creates a serious issue. Consequently, PHEVs emit almost as much as petrol cars.”

Primary Reasons Driving the Emissions Gap

Analysts linked most of the difference to overestimates of the “utility factor” – the percentage of kilometers travelled in battery power relative to overall mileage. They determined that only a quarter of travel was completed in EV mode, whereas official assumptions suggested over four-fifths.

Additionally, when operating in electric mode, pollution levels were well above lab estimates. This happened because electric motors were insufficiently powerful sufficient to function independently, resulting to combustion motors burning gasoline for almost one-third of the travel completed in EV mode.

Regulatory and Economic Consequences

Based on calculations, the underestimation of PHEV CO2 output allowed several major carmaker groups to escape more than €5bn in fines between 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ targets.

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

“The bold claims that manufacturers like to make about their PHEV cars are clearly far from the truth,” commented a transport expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the environment and saving costs. Actually, PHEVs are little better than standard gas and diesel vehicles in terms of energy consumption, CO₂ production, and operating expenses.”

Policy Discussion and Industry Lobbying

Hybrid vehicles have lately been drawn again into political discussions as automakers have pressed the EU to weaken CO₂ targets. A proposed ban on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the automotive sector and resistance from member states with large car manufacturing.

Some senior politicians have suggested PHEVs as a potential “compromise” solution to introduce in the legislation.

An external energy economics specialist, who was unaffiliated with the study, called the analysis a “very useful contribution” after years in which parts of the automotive industry claimed there was insufficient information to accurately evaluate actual emissions.

“These findings demonstrate, without question, that the difference in official and actual PHEV energy use and CO₂ emissions is much, much greater than for petrol or diesel cars,” they said. “All regulatory changes concerning PHEVs should be made with extreme care and considering that evidence.”