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Plug-in hybrid cars produce nearly five times greater planet-heating pollution than official figures show, according to a recent report.

Growing Gap In Lab and Real-World Emissions

Statistics reveals that PHEVs release just 19% lower CO₂ than traditional petrol and diesel vehicles, based on analysis carried out by a non-profit organization. This differs significantly with laboratory estimates, which suggested a 75% decrease in pollution.

Analysts studied data from onboard energy use meters of eight hundred thousand cars sold 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 estimates, increased from three and a half times in 2021.

“Actual emissions are rising, while lab-reported figures are decreasing,” said a senior analyst involved in the study. “That gap is growing and poses a significant problem. Consequently, PHEVs pollute nearly as much as gasoline cars.”

Key Factors Driving the Emissions Gap

Researchers linked most of the gap to inflated estimates of the “utility factor” – the ratio of miles driven in electric power compared to overall distance. The team determined that only 27% of driving was done in electric mode, while official assumptions assumed over four-fifths.

Even, when running in electric mode, pollution amounts were significantly higher than official estimates. That happened because EV motors were insufficiently powerful enough to function alone, leading to engines using gasoline for almost a third of the travel completed in EV mode.

Regulatory and Financial Implications

According to estimates, the underestimation of PHEV emissions enabled several large carmaker groups to avoid over €5bn in penalties between 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs could spend approximately €500 extra per year in running costs than would be estimated under laboratory tests.

“The strong statements that manufacturers often promote about their PHEV vehicles are obviously way off the mark,” commented a transport analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the environment and cutting money. In reality, PHEVs are only slightly improved than regular gas and diesel vehicles in terms of energy use, CO₂ production, and running expenses.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid cars have recently been drawn again into policy debates as automakers have pressed the EU to relax CO₂ targets. A planned prohibition on new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive industry and opposition from EU countries with large automotive manufacturing.

Several high-level politicians have proposed PHEVs as a potential “compromise” solution to introduce in the legislation.

An external energy policy expert, who was unaffiliated with the research, described the analysis a “highly valuable addition” after years in which parts of the car industry claimed there was insufficient data to accurately evaluate real-world emissions.

“The results demonstrate, beyond any doubt, that the difference in official and real-world PHEV energy use and CO₂ output is significantly greater than for gasoline or conventional vehicles,” the expert stated. “All regulatory changes regarding PHEVs should be implemented with utmost care and in the light of this evidence.”