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

Plug-in hybrid electric vehicles produce almost five times greater global warming pollution than official figures show, as per a recent analysis.

Growing Gap Between Official and Actual Emissions

Data reveals that PHEVs release only 19% lower CO₂ than traditional petrol and diesel cars, according to research carried out by a non-profit group. That contrasts significantly with laboratory estimates, which assumed a three-quarters decrease in emissions.

Researchers studied information from in-vehicle fuel consumption monitors of 800,000 vehicles registered in the EU from 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are decreasing,” said a senior analyst participating in the study. “That discrepancy is widening and poses a significant issue. Consequently, PHEVs emit almost as heavily as gasoline vehicles.”

Key Factors Behind the Discrepancy

Researchers attributed the majority of the gap to inflated estimates of the “electric driving share” – the ratio of miles travelled in electric power relative to total mileage. The team found that just 27% of driving was completed in electric mode, while lab assumptions suggested 84%.

Additionally, when operating in EV mode, emission levels were well above official projections. This happened because electric motors were not strong sufficient to function independently, leading to engines using fossil fuels for almost one-third of the travel completed in electric mode.

Policy and Financial Consequences

According to estimates, the underestimation of PHEV emissions allowed several major automaker companies to avoid more than €5bn in fines between 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ targets.

Additionally, owners of PHEVs could spend approximately €500 more annually in operating expenses than is estimated under laboratory tests.

“The strong statements that automakers like to make about their plug-in hybrid vehicles are obviously way off the mark,” stated a automotive expert. “Consumers are being duped into believing that by buying a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are only slightly better than standard gas and diesel cars in terms of fuel consumption, CO₂ production, and running expenses.”

Political Discussion and Automotive Pressure

Hybrid vehicles have recently been drawn back into political debates as automakers have lobbied the EU to weaken CO₂ targets. A proposed prohibition on sales of new combustion engine cars in 2035 has faced intense lobbying from the automotive industry and opposition from member states with significant car manufacturing.

Some high-level politicians have suggested plug-in hybrids as a potential “compromise” solution to include in the regulation.

One external energy policy expert, who was unaffiliated with the study, called the analysis a “highly valuable contribution” after years in which parts of the automotive industry argued there was too little information to accurately assess real-world CO2 output.

“These findings show, beyond any doubt, that the difference between lab and real-world PHEV energy use and CO₂ output is significantly larger than for petrol or conventional cars,” the expert said. “Any policy changes concerning PHEVs should be made with extreme care and considering this data.”