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PHEVs release almost five times greater planet-heating emissions than official figures indicate, according to a new report.

Widening Gap In Official and Actual Emissions

Statistics reveals that PHEVs emit just 19% lower CO₂ than conventional petrol and diesel vehicles, according to analysis conducted by a non-profit group. That contrasts significantly with lab estimates, which assumed a three-quarters decrease in emissions.

Researchers examined data from onboard fuel consumption 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 greater than lab estimates, increased from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported emissions are falling,” stated a lead researcher involved in the report. “This discrepancy is growing and poses a significant issue. As a result, PHEVs emit almost as heavily as petrol vehicles.”

Key Reasons Driving the Emissions Gap

Analysts linked most of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in electric mode compared to total distance. The team determined that just 27% of travel was done in EV mode, whereas official estimates assumed 84%.

Additionally, when running in EV mode, pollution amounts were well above official projections. That happened because electric motors were not strong sufficient to operate independently, leading to engines using fossil fuels for almost one-third of the travel completed in electric mode.

Policy and Economic Implications

Based on calculations, the underestimation of PHEV emissions allowed four large carmaker companies to avoid more than €5bn in fines between 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ standards.

Furthermore, drivers of PHEVs would pay approximately €500 more annually in running expenses than is assumed under laboratory tests.

“The strong claims that manufacturers like to make about their PHEV vehicles are clearly far from the mark,” stated a transport analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are helping the environment and cutting costs. In reality, PHEVs are little improved than standard petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and operating costs.”

Political Debate and Automotive Lobbying

Plug-in hybrid cars have recently been drawn back into policy debates as carmakers have pressed the European Union to weaken CO₂ targets. A planned ban on sales of new internal combustion cars in 2035 has faced intense pressure from the automotive industry and resistance from EU countries with significant automotive manufacturing.

Some senior politicians have proposed PHEVs as a possible “compromise” option to include in the regulation.

One independent energy economics expert, who was not involved with the research, called the report a “highly valuable addition” after a long period in which parts of the automotive sector argued there was too little information to accurately assess real-world emissions.

“These findings show, beyond any doubt, that the gap between official and real-world PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or conventional cars,” the expert said. “Any policy changes concerning PHEVs should be implemented with utmost care and in the light of this evidence.”