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Plug-in hybrid cars produce almost five times more global warming pollution than lab-reported data show, as per a recent report.

Widening Discrepancy In Lab and Real-World Emissions

Statistics shows that PHEVs emit just 19% less CO₂ than traditional petrol and diesel vehicles, according to analysis conducted by a non-profit group. This differs sharply with laboratory estimates, which assumed a three-quarters reduction in pollution.

Researchers studied data from in-vehicle fuel consumption monitors of eight hundred thousand vehicles registered in the EU between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported figures are falling,” stated a lead analyst involved in the report. “That gap is widening and creates a significant issue. Consequently, PHEVs pollute almost as heavily as petrol vehicles.”

Primary Factors Behind the Discrepancy

Analysts attributed the majority of the difference to inflated estimates of the “utility factor” – the ratio of miles driven in battery mode compared to overall mileage. The team found that only 27% of travel was completed in EV mode, whereas lab assumptions suggested over four-fifths.

Additionally, when running in EV mode, emission levels were significantly higher than lab projections. That happened because EV motors were insufficiently powerful enough to function independently, resulting to engines burning gasoline for nearly a third of the travel covered in EV mode.

Regulatory and Economic Consequences

According to calculations, the underestimation of PHEV CO2 output enabled several large carmaker companies to escape over €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would pay approximately €500 extra annually in running costs than is estimated under lab conditions.

“The strong claims that automakers often promote about their PHEV cars are obviously way off the truth,” stated a automotive analyst. “Buyers are being duped into believing that by buying a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are little improved than regular petrol and diesel cars in terms of fuel consumption, CO₂ production, and running costs.”

Policy Debate and Automotive Lobbying

Hybrid cars have recently been brought again into policy discussions as carmakers have lobbied the EU to weaken CO₂ standards. A proposed prohibition on new combustion engine vehicles in 2035 has faced intense lobbying from the automotive sector and opposition from member states with large automotive manufacturing.

Some high-level officials have proposed PHEVs as a potential “compromise” solution to introduce in the regulation.

An external energy economics expert, who was not involved with the research, called the report a “highly valuable addition” after years in which parts of the automotive industry claimed there was insufficient data to accurately evaluate real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the gap in lab and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for gasoline or conventional vehicles,” the expert said. “All regulatory changes regarding PHEVs should be implemented with extreme caution and in the light of that evidence.”