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Plug-in hybrid electric vehicles release nearly 5x more planet-heating emissions than official figures indicate, as per a new analysis.

Growing Discrepancy Between Official and Real-World CO2 Output

Statistics shows that PHEVs emit only one-fifth lower CO₂ than conventional gas and diesel cars, according to research carried out by a non-profit organization. That differs sharply with laboratory tests, which assumed a 75% reduction in pollution.

Analysts examined information from onboard energy use monitors of 800,000 cars sold in the EU between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than official figures, up from three and a half times in 2021.

“Real-world emissions are rising, while official figures are decreasing,” stated a senior researcher participating in the study. “This gap is widening and creates a serious issue. As a result, PHEVs pollute almost as heavily as petrol vehicles.”

Primary Factors Behind the Discrepancy

Researchers linked the majority of the gap to inflated estimates of the “utility factor” – the percentage of miles travelled in battery power relative to overall mileage. They found that just a quarter of driving was done in electric mode, whereas official assumptions assumed over four-fifths.

Additionally, when running in EV mode, emission levels were significantly higher than lab projections. That occurred because electric motors were not strong enough to operate independently, leading to combustion motors using fossil fuels for nearly a third of the travel completed in electric mode.

Regulatory and Economic Implications

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

Additionally, drivers of PHEVs could pay approximately €500 more annually in operating expenses than is assumed under laboratory tests.

“The strong claims that manufacturers often promote about their plug-in hybrid cars are obviously far from the mark,” stated a automotive analyst. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are little better than standard gas and diesel vehicles in terms of energy consumption, CO₂ production, and running costs.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid cars have recently been drawn again into political discussions as automakers have pressed the EU to weaken CO₂ standards. A planned prohibition on new combustion engine vehicles in 2035 has faced intense pressure from the automotive industry and resistance from EU countries with large automotive industries.

Several high-level officials have suggested plug-in hybrids as a possible “compromise” solution to include in the legislation.

One external energy economics expert, who was unaffiliated with the study, called the analysis a “very useful contribution” after years in which parts of the automotive sector claimed there was insufficient data to accurately evaluate real-world CO2 output.

“These findings show, beyond any doubt, that the difference in lab and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for gasoline or diesel cars,” the expert said. “All policy adjustments concerning PHEVs should be made with extreme caution and considering that data.”