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Plug-in hybrid electric vehicles emit nearly five times more planet-heating pollution than lab-reported figures show, as per a new report.

Growing Gap In Official and Actual CO2 Output

Data shows that PHEVs release only 19% lower CO₂ than traditional gas and diesel vehicles, according to analysis carried out by a non-profit group. This differs sharply with laboratory estimates, which suggested a three-quarters reduction in pollution.

Analysts studied data from in-vehicle energy use meters of 800,000 cars sold in Europe from 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from three and a half times in 2021.

“Real-world emissions are increasing, while official figures are falling,” said a senior analyst participating in the study. “That discrepancy is widening and poses a significant problem. Consequently, PHEVs pollute almost as heavily as gasoline vehicles.”

Key Factors Driving the Emissions Gap

Analysts linked the majority of the difference to overestimates of the “electric driving share” – the percentage of miles driven in electric power relative to total distance. They determined that only a quarter of driving was done in electric mode, while lab estimates suggested 84%.

Additionally, when running in EV mode, emission levels were significantly higher than official projections. That happened because EV motors were not strong sufficient to operate alone, resulting to combustion motors burning fossil fuels for almost a third of the distance covered in electric mode.

Regulatory and Economic Consequences

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

Additionally, drivers of PHEVs could pay approximately €500 more annually in operating costs than would be estimated under laboratory conditions.

“The bold statements that automakers like to make about their PHEV cars are obviously way off the mark,” stated a transport expert. “Buyers are being misled into thinking that by buying a PHEV, they are helping the environment and cutting costs. In reality, PHEVs are little better than regular petrol and diesel vehicles in terms of energy use, CO₂ production, and operating costs.”

Policy Debate and Automotive Lobbying

Hybrid cars have lately been brought back into political debates as automakers have pressed the EU to relax CO₂ targets. A proposed prohibition on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the car industry and resistance from EU countries with significant automotive manufacturing.

Several high-level politicians have proposed plug-in hybrids as a potential “flexibility” option to introduce in the legislation.

An independent energy policy expert, who was not involved with the research, described the report a “very useful contribution” after a long period in which segments of the car industry claimed there was too little information to properly evaluate actual CO2 output.

“These findings demonstrate, beyond any doubt, that the gap between official and real-world PHEV energy use and CO₂ emissions is much, much larger than for petrol or diesel cars,” the expert said. “Any regulatory adjustments concerning PHEVs should be made with extreme caution and in the light of this data.”