🔗 Share this article

Plug-in hybrid cars emit nearly five times more planet-heating pollution than lab-reported data show, according to a new report.

Growing Gap Between Official and Real-World Emissions

Statistics shows that PHEVs emit just one-fifth lower CO₂ than traditional petrol and diesel cars, according to research carried out by a advocacy group. That contrasts sharply with lab estimates, which suggested a three-quarters reduction in emissions.

Analysts examined data from onboard energy use monitors of eight hundred thousand vehicles registered in Europe from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab figures, up from three and a half times in 2021.

“Actual emissions are rising, while official figures are falling,” said a senior researcher involved in the study. “That discrepancy is growing and poses a serious problem. As a result, PHEVs emit nearly as heavily as petrol cars.”

Primary Factors Driving the Emissions Gap

Researchers linked most of the difference to inflated estimates of the “utility factor” – the ratio of miles travelled in battery mode compared to overall mileage. They found that just 27% of travel was completed in electric mode, while official assumptions suggested over four-fifths.

Even, when running in EV mode, emission levels were significantly higher than official estimates. That occurred because electric motors were not strong sufficient to function independently, leading to engines burning fossil fuels for nearly a third of the travel completed in electric mode.

Regulatory and Economic Consequences

Based on calculations, the underestimation of PHEV emissions allowed four large automaker groups to avoid over €5bn in penalties between 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ standards.

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

“The bold statements that automakers like to make about their PHEV cars are clearly way off the mark,” commented a automotive expert. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are little better than regular petrol and diesel cars in terms of energy consumption, CO₂ production, and running costs.”

Policy Debate and Industry Pressure

Hybrid cars have lately been drawn back into policy debates as carmakers have lobbied the European Union to weaken CO₂ targets. A proposed ban on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the car industry and resistance from EU countries with large automotive manufacturing.

Several high-level officials have suggested PHEVs as a potential “flexibility” solution to include in the regulation.

An external energy economics expert, who was not involved with the research, described the analysis a “very useful addition” after a long period in which parts of the car industry argued there was too little information to properly assess real-world emissions.

“The results demonstrate, without question, that the difference between official and actual PHEV energy use and CO₂ emissions is much, much greater than for petrol or conventional cars,” they said. “All regulatory adjustments concerning PHEVs should be made with extreme care and considering this data.”