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Plug-in hybrid electric vehicles emit nearly five times more global warming pollution than lab-reported figures indicate, according to a recent analysis.

Growing Discrepancy Between Official and Actual CO2 Output

Data shows that PHEVs release only 19% lower CO₂ than conventional petrol and diesel cars, based on analysis conducted by a advocacy organization. That differs significantly with lab estimates, which suggested a three-quarters reduction in pollution.

Analysts studied information from in-vehicle fuel consumption monitors of eight hundred thousand vehicles sold in the EU from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, increased from three and a half times in 2021.

“Real-world emissions are increasing, while official emissions are falling,” stated a senior analyst involved in the report. “That gap is growing and creates a significant problem. Consequently, PHEVs pollute almost as heavily as petrol vehicles.”

Primary Reasons Behind the Discrepancy

Researchers attributed the majority of the difference to overestimates of the “utility factor” – the ratio of miles travelled in battery power compared to overall distance. The team determined that only a quarter of travel was done in EV mode, whereas lab assumptions assumed over four-fifths.

Even, when operating in EV mode, pollution amounts were significantly higher than official estimates. That happened because electric motors were not strong enough to function alone, resulting to combustion motors using gasoline for almost a third of the distance completed in EV mode.

Policy and Financial Consequences

According to calculations, the underestimation of PHEV CO2 output allowed several major carmaker companies to escape over €5bn in penalties between 2021 and 2023, by artificially easing adherence with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs could spend approximately €500 more per year in running costs than is assumed under lab tests.

“The strong claims that automakers often promote about their plug-in hybrid cars are clearly way off the truth,” commented a transport expert. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are only slightly better than regular gas and diesel cars in terms of fuel consumption, CO₂ production, and operating expenses.”

Policy Discussion and Industry Lobbying

Plug-in hybrid vehicles have lately been brought back into political debates as automakers have lobbied the European Union to relax CO₂ standards. A planned ban on new internal combustion cars in 2035 has faced heavy lobbying from the car sector and opposition from member states with significant car manufacturing.

Some senior officials have suggested plug-in hybrids as a potential “flexibility” solution to introduce in the regulation.

One external energy economics expert, who was unaffiliated with the research, described the report a “highly valuable contribution” after years in which parts of the automotive sector claimed there was insufficient data to properly evaluate real-world CO2 output.

“These findings show, beyond any doubt, that the gap in official and actual PHEV fuel consumption and CO₂ output is significantly larger than for petrol or diesel cars,” they said. “All regulatory changes regarding PHEVs should be made with utmost care and considering that data.”