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Plug-in hybrid electric vehicles release almost 5x more global warming pollution than lab-reported data indicate, according to a new analysis.

Widening Discrepancy In Official and Real-World Emissions

Data shows that PHEVs emit only one-fifth lower CO₂ than conventional gas and diesel vehicles, based on analysis carried out by a non-profit group. This contrasts significantly with laboratory tests, which suggested a three-quarters decrease in emissions.

Analysts examined data from onboard energy use monitors of 800,000 cars registered in Europe between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab estimates, up from three and a half times in 2021.

“Real-world CO2 output are rising, while official figures are falling,” said a senior researcher involved in the study. “That gap is growing and poses a serious issue. Consequently, PHEVs pollute nearly as heavily as petrol cars.”

Primary Factors Driving the Discrepancy

Analysts attributed the majority of the gap to inflated estimates of the “utility factor” – the percentage of miles travelled in battery power relative to overall distance. They determined that just 27% of driving was done in EV mode, while lab assumptions suggested over four-fifths.

Even, when operating in electric mode, pollution levels were well above lab estimates. That occurred because electric motors were not strong sufficient to function independently, leading to combustion motors using gasoline for almost one-third of the distance completed in electric mode.

Regulatory and Economic Consequences

Based on estimates, the lowballing of PHEV emissions allowed several major automaker groups to avoid more than €5bn in penalties from 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ targets.

Furthermore, owners of PHEVs could pay approximately €500 extra per year in running costs than would be assumed under lab conditions.

“The strong claims that manufacturers often promote about their PHEV vehicles are clearly way off the truth,” commented a automotive analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are little better than regular petrol and diesel cars in terms of fuel consumption, CO₂ production, and operating expenses.”

Policy Debate and Automotive Lobbying

Hybrid vehicles have lately been brought again into political debates as automakers have lobbied the EU to relax CO₂ targets. A planned prohibition on new internal combustion vehicles in 2035 has faced intense pressure from the car industry and opposition from member states with large car manufacturing.

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

One independent energy policy specialist, who was unaffiliated with the research, described the report a “very useful addition” after a long period in which parts of the automotive industry argued there was too little data to accurately assess actual emissions.

“The results demonstrate, without question, that the difference in lab and real-world PHEV energy use and CO₂ output is much, much greater than for gasoline or diesel cars,” the expert stated. “Any regulatory adjustments concerning PHEVs should be made with extreme care and considering that data.”