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Plug-in hybrid cars release nearly five times greater planet-heating pollution than official data indicate, according to a new analysis.

Growing Discrepancy In Official and Actual Emissions

Data reveals that PHEVs release only 19% less CO₂ than traditional gas and diesel cars, based on research carried out by a non-profit organization. This contrasts significantly with lab estimates, which suggested a 75% reduction in pollution.

Analysts studied information from in-vehicle energy use monitors of 800,000 cars sold in the EU from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official figures, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while official figures are decreasing,” stated a senior analyst involved in the report. “That gap is widening and creates a serious issue. Consequently, PHEVs emit nearly as much as petrol vehicles.”

Primary Reasons Driving the Emissions Gap

Analysts attributed the majority of the difference to overestimates of the “utility factor” – the percentage of miles travelled in battery mode compared to total distance. They determined that just 27% of travel was done in electric mode, while official assumptions assumed 84%.

Even, when operating in electric mode, pollution levels were significantly higher than official estimates. That happened because EV motors were not strong sufficient to operate alone, resulting to engines using gasoline for nearly one-third of the travel completed in electric mode.

Regulatory and Financial Implications

According to calculations, the underestimation of PHEV emissions allowed several major automaker companies to escape over €5bn in penalties from 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ standards.

Furthermore, drivers of PHEVs could pay about €500 extra per year in operating expenses than is assumed under lab tests.

“The strong claims that manufacturers like to make about their PHEV vehicles are obviously far from the truth,” commented a automotive expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are little better than regular petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating expenses.”

Political Debate and Industry Pressure

Plug-in hybrid vehicles have recently been brought again into policy debates as automakers have pressed the EU to weaken CO₂ targets. A proposed ban on sales of new combustion engine vehicles in 2035 has faced intense pressure from the automotive industry and opposition from EU countries with significant automotive manufacturing.

Several senior politicians have suggested plug-in hybrids as a potential “flexibility” option to include in the legislation.

One external energy policy expert, who was unaffiliated with the study, described the analysis a “highly valuable contribution” after years in which segments of the automotive sector argued there was too little information to accurately evaluate real-world emissions.

“The results demonstrate, beyond any doubt, that the difference between official and actual PHEV energy use and CO₂ output is much, much larger than for gasoline or diesel vehicles,” they said. “All regulatory adjustments concerning PHEVs should be implemented with extreme caution and in the light of that data.”