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Plug-in hybrid electric vehicles emit nearly five times more global warming pollution than lab-reported data indicate, according to a recent report.

Growing Discrepancy In Official and Real-World Emissions

Statistics shows that PHEVs emit just 19% less CO₂ than conventional petrol and diesel vehicles, according to research conducted by a non-profit organization. This contrasts significantly with lab tests, which assumed a 75% reduction in emissions.

Analysts examined data from in-vehicle fuel consumption meters of 800,000 cars registered in the EU from 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are decreasing,” stated a senior researcher involved in the study. “That discrepancy is growing and creates a serious problem. Consequently, PHEVs emit almost as much as petrol cars.”

Primary Factors Behind the Discrepancy

Analysts attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of miles driven in battery power relative to overall mileage. The team determined that just a quarter of driving was done in electric mode, whereas official assumptions suggested over four-fifths.

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

Regulatory and Financial Consequences

Based on estimates, the lowballing of PHEV emissions allowed several large carmaker groups to escape over €5bn in fines from 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ targets.

Additionally, drivers of PHEVs could spend approximately €500 more annually in running costs than is estimated under lab tests.

“The strong statements that automakers often promote about their plug-in hybrid vehicles are clearly way off the mark,” stated a transport analyst. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are little better than standard petrol and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running expenses.”

Policy Discussion and Industry Lobbying

Plug-in hybrid cars have recently been brought again into political debates as carmakers have pressed the EU to relax CO₂ standards. A planned ban on new internal combustion vehicles in 2035 has faced heavy lobbying from the car industry and opposition from member states with large automotive industries.

Several high-level officials have suggested plug-in hybrids as a possible “flexibility” option to include in the regulation.

An external energy policy specialist, who was not involved with the research, described the report a “very useful addition” after years in which parts of the automotive industry claimed there was too little data to properly assess real-world emissions.

“The results demonstrate, without question, that the difference between official and actual PHEV fuel consumption and CO₂ emissions is significantly greater than for petrol or diesel cars,” they stated. “All regulatory adjustments concerning PHEVs should be implemented with utmost care and in the light of that data.”