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Plug-in hybrid electric vehicles release almost 5x more global warming pollution than official figures indicate, according to a new analysis.

Growing Discrepancy In Lab and Real-World CO2 Output

Data reveals that PHEVs release just 19% lower CO₂ than traditional gas and diesel cars, according to research conducted by a non-profit group. That differs significantly with lab tests, which assumed a three-quarters reduction in pollution.

Analysts studied information from in-vehicle fuel consumption monitors of eight hundred thousand cars registered in Europe between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times greater than official estimates, up from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are falling,” stated a lead researcher participating in the report. “This discrepancy is widening and poses a significant issue. Consequently, PHEVs pollute nearly as heavily as petrol vehicles.”

Primary Factors Behind the Discrepancy

Researchers attributed most of the difference to inflated estimates of the “utility factor” – the ratio of miles travelled in battery mode relative to total mileage. The team determined that only 27% of driving was done in EV mode, whereas lab assumptions assumed 84%.

Additionally, when running in electric mode, emission levels were significantly higher than lab estimates. That happened because EV motors were not strong enough to function independently, leading to engines burning fossil fuels for nearly one-third of the travel completed in EV mode.

Regulatory and Economic Implications

According to calculations, the lowballing of PHEV CO2 output enabled several large carmaker groups to avoid more than €5bn in fines from 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would pay approximately €500 extra per year in running expenses than is estimated under lab tests.

“The bold claims that automakers often promote about their plug-in hybrid vehicles are clearly far from the truth,” commented a automotive expert. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are little better than regular petrol and diesel vehicles in terms of energy consumption, CO₂ production, and operating costs.”

Policy Discussion and Automotive Lobbying

Hybrid cars have lately been drawn back into policy discussions as automakers have lobbied the EU to relax CO₂ targets. A proposed prohibition on new combustion engine cars in 2035 has faced heavy lobbying from the car sector and resistance from EU countries with large automotive manufacturing.

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

One independent energy economics specialist, who was not involved with the research, called the report a “very useful contribution” after years in which segments of the automotive industry claimed there was insufficient information to properly assess actual CO2 output.

“These findings demonstrate, without question, that the gap between lab and actual PHEV energy use and CO₂ emissions is significantly larger than for petrol or diesel vehicles,” the expert stated. “Any policy changes regarding PHEVs should be implemented with utmost care and considering that evidence.”