Plug-in Hybrid Cars Pollute Nearly as Much as Gasoline Cars, Report Finds

PHEVs produce nearly five times more global warming pollution than lab-reported data indicate, according to a new report.

Growing Gap In Lab and Actual Emissions

Data reveals that PHEVs emit just one-fifth less CO₂ than traditional petrol and diesel vehicles, according to analysis carried out by a non-profit organization. This differs sharply with lab tests, which assumed a three-quarters reduction in emissions.

Researchers studied data from in-vehicle energy use meters of eight hundred thousand cars sold in the EU between 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, increased from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported figures are falling,” said a lead researcher involved in the study. “That discrepancy is growing and poses a significant problem. Consequently, PHEVs pollute almost as much as petrol cars.”

Key Factors Driving the Discrepancy

Analysts attributed the majority of the difference to overestimates of the “electric driving share” – the percentage of miles driven in electric power relative to overall distance. They determined that only a quarter of travel was completed in electric mode, while lab assumptions suggested 84%.

Even, when operating in electric mode, emission amounts were significantly higher than lab projections. That occurred because EV motors were insufficiently powerful sufficient to operate independently, resulting to engines burning fossil fuels for nearly a third of the travel completed in EV mode.

Regulatory and Economic Consequences

According to estimates, the underestimation of PHEV CO2 output allowed four large automaker groups to avoid over €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ standards.

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

“The bold statements that automakers like to make about their plug-in hybrid vehicles are obviously way off the truth,” commented a transport expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are only slightly better than regular petrol and diesel vehicles in terms of fuel consumption, CO₂ production, and running costs.”

Policy Debate and Industry Pressure

Plug-in hybrid vehicles have recently been drawn again into political discussions as automakers have lobbied the European Union to weaken CO₂ targets. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced intense lobbying from the automotive sector and opposition from EU countries with large automotive manufacturing.

Some senior officials have proposed plug-in hybrids as a potential “compromise” option to introduce in the legislation.

One external energy economics specialist, who was not involved with the study, called the report a “very useful addition” after years in which parts of the automotive sector claimed there was insufficient data to properly assess actual CO2 output.

“The results demonstrate, beyond any doubt, that the difference between lab and real-world PHEV fuel consumption and CO₂ output is significantly larger than for petrol or diesel cars,” they said. “All policy changes concerning PHEVs should be made with utmost caution and in the light of that evidence.”