Plug-in Hybrid Vehicles Emit Almost as Heavily as Petrol Cars, Report Finds

Plug-in hybrid cars release nearly five times more planet-heating pollution than lab-reported figures indicate, according to a new analysis.

Widening Gap Between Official and Real-World CO2 Output

Data reveals that PHEVs release just 19% less CO₂ than conventional gas and diesel vehicles, according to analysis carried out by a advocacy group. That differs significantly with laboratory estimates, which suggested a three-quarters decrease in pollution.

Researchers studied data from onboard energy use monitors of eight hundred thousand cars registered in Europe from 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, increased from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported emissions are decreasing,” said a lead researcher participating in the report. “This discrepancy is widening and poses a significant problem. Consequently, PHEVs pollute almost as much as gasoline vehicles.”

Primary Factors Behind the Emissions Gap

Analysts attributed most of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in battery mode compared to overall distance. They determined that only a quarter of travel was completed in electric mode, whereas official assumptions suggested 84%.

Additionally, when operating in electric mode, emission levels were significantly higher than official projections. That occurred because electric motors were not strong enough to operate alone, resulting to combustion motors burning fossil fuels for almost a third of the distance completed in electric mode.

Policy and Financial Implications

Based on estimates, the underestimation of PHEV CO2 output enabled four large automaker groups to avoid over €5bn in penalties from 2021 and 2023, by artificially easing adherence with EU average fleet CO₂ targets.

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

“The strong statements that automakers like to make about their PHEV vehicles are obviously far from the truth,” stated a transport analyst. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are little improved than regular petrol and diesel cars in terms of energy use, CO₂ emissions, and running costs.”

Policy Debate and Industry Pressure

Hybrid vehicles have recently been brought back into political debates as carmakers have pressed the EU to weaken CO₂ targets. A proposed ban on new internal combustion cars in 2035 has faced intense pressure from the car industry and opposition from member states with significant car manufacturing.

Several senior politicians have suggested plug-in hybrids as a potential “compromise” option to introduce in the regulation.

One independent energy economics expert, who was unaffiliated with the research, called the analysis a “very useful contribution” after a long period in which segments of the automotive industry claimed there was insufficient data to accurately assess actual CO2 output.

“The results demonstrate, beyond any doubt, that the difference between lab and real-world PHEV energy use and CO₂ emissions is much, much greater than for gasoline or diesel vehicles,” they said. “All policy adjustments regarding PHEVs should be implemented with extreme caution and considering this data.”