Plug in Hybrid Vehicles Emit Almost as Much as Petrol Cars, Study Finds

Plug-in hybrid cars produce almost 5x more planet-heating emissions than official figures indicate, according to a recent report.

Widening Gap Between Official and Actual Emissions

Statistics shows that PHEVs release only 19% less CO₂ than conventional gas and diesel cars, based on analysis carried out by a advocacy group. This contrasts sharply with lab tests, which suggested a 75% reduction in pollution.

Researchers examined data from onboard energy use monitors of eight hundred thousand cars registered in the EU from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, up from three and a half times in 2021.

“Actual CO2 output are increasing, while official emissions are decreasing,” said a lead researcher involved in the study. “That discrepancy is widening and poses a serious problem. As a result, PHEVs pollute nearly as heavily as gasoline cars.”

Primary Factors Behind the Discrepancy

Analysts attributed the majority of the gap to overestimates of the “electric driving share” – the ratio of miles travelled in battery mode relative to total distance. They found that only a quarter of travel was completed in electric mode, whereas lab estimates assumed over four-fifths.

Additionally, when running in EV mode, emission amounts were significantly higher than official projections. That happened because electric motors were insufficiently powerful sufficient to function independently, resulting to engines using gasoline for nearly one-third of the travel covered in EV mode.

Policy and Financial Implications

Based on estimates, the underestimation of PHEV CO2 output allowed several large carmaker companies to avoid over €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs could pay about €500 extra per year in running costs than is assumed under lab tests.

“The strong statements that automakers like to make about their plug-in hybrid cars are clearly far from the mark,” stated a transport expert. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are only slightly better than standard gas and diesel vehicles in terms of energy consumption, CO₂ emissions, and running expenses.”

Policy Discussion and Automotive Lobbying

Hybrid cars have recently been drawn back into policy discussions as carmakers have pressed the European Union to relax CO₂ standards. A proposed prohibition on sales of new combustion engine cars in 2035 has faced heavy lobbying from the automotive industry and opposition from member states with significant car manufacturing.

Some senior politicians have suggested plug-in hybrids as a possible “flexibility” solution to include in the regulation.

One external energy policy specialist, who was not involved with the study, called the report a “very useful contribution” after years in which parts of the car industry argued there was insufficient data to accurately evaluate actual CO2 output.

“These findings show, beyond any doubt, that the difference in official and real-world PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or conventional cars,” the expert stated. “Any policy changes regarding PHEVs should be made with extreme care and in the light of this data.”