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PHEVs release almost 5x more global warming pollution than official figures indicate, as per a new report.

Growing Gap Between Lab and Actual CO2 Output

Data reveals that PHEVs release just one-fifth lower CO₂ than traditional petrol and diesel vehicles, according to analysis carried out by a non-profit organization. That contrasts sharply with lab tests, which suggested a three-quarters reduction in pollution.

Researchers examined information from in-vehicle energy use monitors of 800,000 cars sold in the EU between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, up from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are falling,” stated a senior analyst involved in the study. “That discrepancy is growing and creates a serious problem. Consequently, PHEVs pollute nearly as much as gasoline vehicles.”

Key Reasons Driving the Emissions Gap

Analysts attributed most of the difference to overestimates of the “utility factor” – the ratio of kilometers driven in battery power compared to total mileage. They found that only 27% of travel was completed in EV mode, while official assumptions suggested over four-fifths.

Additionally, when running in electric mode, emission levels were significantly higher than official projections. That occurred because EV motors were insufficiently powerful enough to function independently, leading to engines using fossil fuels for almost a third of the distance covered in EV mode.

Policy and Financial Consequences

Based on calculations, the underestimation of PHEV CO2 output allowed four 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, drivers of PHEVs could spend approximately €500 extra per year in running costs than is estimated under lab tests.

“The strong claims that manufacturers like to make about their plug-in hybrid cars are clearly far from the truth,” commented a transport expert. “Consumers are being misled into thinking that by buying a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are little improved than standard petrol and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running expenses.”

Political Debate and Industry Pressure

Plug-in hybrid vehicles have lately been brought again into policy discussions as automakers have lobbied the European Union to relax CO₂ targets. A proposed prohibition on sales of new combustion engine cars in 2035 has faced intense lobbying from the car sector and opposition from EU countries with significant automotive industries.

Several high-level officials have proposed PHEVs as a possible “compromise” option to include in the legislation.

One independent energy policy specialist, who was unaffiliated with the research, called the analysis a “highly valuable addition” after a long period in which segments of the car sector argued there was insufficient information to accurately evaluate actual emissions.

“The results demonstrate, without question, that the gap between official and real-world PHEV energy use and CO₂ emissions is significantly larger than for petrol or diesel cars,” the expert said. “All policy changes regarding PHEVs should be made with extreme caution and in the light of this evidence.”