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Plug-in hybrid cars produce almost five times more planet-heating pollution than official data show, according to a recent analysis.

Widening Gap In Official and Actual Emissions

Data reveals that PHEVs emit only 19% less CO₂ than conventional petrol and diesel vehicles, based on research conducted by a non-profit group. That contrasts sharply with lab tests, which suggested a 75% decrease in emissions.

Researchers studied information from onboard fuel consumption meters of eight hundred thousand cars registered in Europe from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, up from three and a half times in 2021.

“Actual emissions are rising, while lab-reported figures are decreasing,” said a lead analyst participating in the report. “This gap is growing and creates a significant problem. As a result, PHEVs pollute nearly as much as petrol vehicles.”

Primary Reasons Driving the Discrepancy

Researchers linked the majority of the gap to overestimates of the “electric driving share” – the percentage of miles travelled in battery mode relative to overall mileage. They found that only 27% of driving was completed in electric mode, while official estimates assumed over four-fifths.

Even, when running in electric mode, emission levels were well above lab estimates. This happened because EV motors were not strong enough to operate independently, leading to combustion motors burning fossil fuels for nearly one-third of the travel completed in electric mode.

Policy and Financial Consequences

Based on calculations, the lowballing of PHEV emissions enabled four large automaker companies to escape more than €5bn in fines between 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs could spend about €500 extra per year in operating costs than would be estimated under lab conditions.

“The strong claims that automakers often promote about their PHEV cars are obviously far from the truth,” commented a automotive expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are only slightly better than regular petrol and diesel vehicles in terms of energy consumption, CO₂ production, and operating expenses.”

Policy Debate and Automotive Pressure

Hybrid vehicles have lately been brought again into policy debates as carmakers have lobbied the European Union to weaken CO₂ standards. A proposed ban on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the car industry and opposition from EU countries with significant car manufacturing.

Some senior officials have proposed plug-in hybrids as a possible “compromise” solution to include in the regulation.

One independent energy policy specialist, who was unaffiliated with the research, described the analysis a “very useful addition” after years in which segments of the car industry argued there was too little data to accurately evaluate actual emissions.

“The results show, beyond any doubt, that the difference in official and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or conventional cars,” they said. “All regulatory adjustments regarding PHEVs should be made with extreme care and considering that evidence.”