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Plug-in hybrid cars produce almost five times greater planet-heating pollution than official figures indicate, as per a recent report.

Growing Gap Between Official and Actual CO2 Output

Data shows that PHEVs emit just 19% less CO₂ than traditional petrol and diesel cars, based on research conducted by a non-profit group. This differs sharply with laboratory tests, which suggested a three-quarters reduction in emissions.

Researchers studied information from onboard fuel consumption meters of 800,000 vehicles sold in Europe between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, up from three and a half times in 2021.

“Actual CO2 output are increasing, while official emissions are decreasing,” stated a lead analyst involved in the report. “That gap is widening and poses a serious problem. Consequently, PHEVs emit nearly as much as gasoline cars.”

Primary Factors Behind the Discrepancy

Analysts attributed the majority of the difference to overestimates of the “utility factor” – the ratio of miles travelled in electric mode relative to total mileage. The team determined that just 27% of travel was completed in electric mode, whereas official estimates assumed over four-fifths.

Additionally, when operating in electric mode, pollution levels were significantly higher than lab projections. This happened because EV motors were not strong sufficient to operate independently, leading to combustion motors burning fossil fuels for nearly one-third of the travel covered in electric mode.

Regulatory and Economic Implications

Based on calculations, the underestimation of PHEV CO2 output enabled four large automaker groups to escape over €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs would pay approximately €500 more per year in operating costs than would be estimated under laboratory tests.

“The strong claims that automakers like to make about their plug-in hybrid vehicles are clearly far from the truth,” commented a transport analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are only slightly better than standard gas and diesel vehicles in terms of energy use, CO₂ production, and running costs.”

Policy Discussion and Industry Pressure

Hybrid vehicles have lately been drawn back into political debates as automakers have lobbied the EU to weaken CO₂ targets. A planned prohibition on sales of new combustion engine cars in 2035 has faced intense pressure from the automotive sector and resistance from member states with significant car manufacturing.

Some senior officials have proposed PHEVs as a possible “compromise” option to introduce in the regulation.

One external energy economics specialist, who was unaffiliated with the study, described the analysis a “highly valuable contribution” after a long period in which parts of the automotive industry claimed there was insufficient information to accurately assess real-world CO2 output.

“The results show, without question, that the difference between official and real-world PHEV energy use and CO₂ output is much, much larger than for gasoline or diesel cars,” they stated. “All regulatory adjustments concerning PHEVs should be implemented with extreme care and considering this evidence.”