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Plug-in hybrid cars release almost 5x more planet-heating pollution than official figures show, according to a new analysis.

Growing Gap Between Official and Actual Emissions

Data reveals that PHEVs release just 19% less CO₂ than conventional gas and diesel cars, according to analysis carried out by a advocacy group. This contrasts sharply with lab tests, which suggested a three-quarters reduction in pollution.

Researchers examined information from onboard energy use meters of 800,000 cars sold in Europe between 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab estimates, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while official figures are decreasing,” stated a senior researcher involved in the study. “That gap is growing and creates a significant issue. Consequently, PHEVs pollute almost as heavily as petrol vehicles.”

Primary Factors Behind the Emissions Gap

Researchers linked the majority of the gap to inflated estimates of the “electric driving share” – the ratio of miles driven in electric power relative to overall distance. The team determined that just 27% of driving was completed in electric mode, while official estimates assumed 84%.

Additionally, when running in electric mode, emission amounts were well above lab estimates. That happened because EV motors were not strong sufficient to function independently, resulting to combustion motors using gasoline for almost one-third of the distance completed in electric mode.

Regulatory and Economic Consequences

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

Furthermore, owners of PHEVs would pay approximately €500 more annually in operating expenses than is estimated under laboratory conditions.

“The strong statements that manufacturers like to make about their PHEV cars are obviously way off the truth,” commented a automotive analyst. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are little improved than standard petrol and diesel cars in terms of energy use, CO₂ production, and running expenses.”

Political Debate and Industry Lobbying

Hybrid cars have recently been brought again into policy discussions as carmakers have lobbied the European Union to weaken CO₂ targets. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the automotive industry and resistance from EU countries with significant automotive manufacturing.

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

One independent energy policy expert, who was not involved with the research, described the analysis a “highly valuable contribution” after a long period in which parts of the automotive industry argued there was too little data to properly assess actual CO2 output.

“The results demonstrate, beyond any doubt, that the gap between lab and actual PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or diesel cars,” they said. “All regulatory adjustments concerning PHEVs should be made with extreme care and in the light of that data.”