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Plug-in hybrid electric vehicles release nearly five times more global warming emissions than lab-reported data show, according to a recent report.

Widening Gap In Official and Real-World CO2 Output

Data shows that PHEVs emit only one-fifth less CO₂ than conventional petrol and diesel cars, according to research carried out by a advocacy organization. This differs significantly with laboratory tests, which suggested a three-quarters decrease in emissions.

Analysts examined data from onboard energy use monitors of 800,000 cars sold in the EU from 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, up from 3.5 times in 2021.

“Real-world CO2 output are rising, while official figures are decreasing,” said a lead analyst involved in the report. “That gap is growing and poses a serious issue. As a result, PHEVs pollute nearly as much as gasoline cars.”

Primary Factors Behind the Discrepancy

Analysts linked the majority of the gap to overestimates of the “electric driving share” – the ratio of kilometers travelled in electric mode relative to total distance. They found that only a quarter of driving was completed in EV mode, while official assumptions suggested over four-fifths.

Additionally, when operating in EV mode, emission amounts were significantly higher than official estimates. This happened because electric motors were insufficiently powerful sufficient to operate independently, leading to combustion motors burning gasoline for nearly one-third of the travel completed in electric mode.

Regulatory and Financial Consequences

According to estimates, the lowballing of PHEV emissions allowed several major carmaker companies to avoid more than €5bn in fines from 2021 and 2023, by artificially easing adherence with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs could spend approximately €500 extra annually in running expenses than would be assumed under laboratory tests.

“The strong statements that manufacturers often promote about their plug-in hybrid vehicles are clearly way off the mark,” stated a automotive expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are little better than regular gas and diesel vehicles in terms of fuel use, CO₂ emissions, and running expenses.”

Policy Discussion and Automotive Pressure

Plug-in hybrid cars have recently been brought again into political discussions as automakers have pressed the European Union to weaken CO₂ standards. A planned ban on new internal combustion cars in 2035 has faced heavy pressure from the car sector and opposition from EU countries with large car manufacturing.

Several senior officials have suggested PHEVs as a potential “compromise” option to include in the legislation.

One independent energy economics specialist, who was unaffiliated with the study, described the analysis a “highly valuable addition” after years in which parts of the automotive industry argued there was too little data to properly evaluate real-world CO2 output.

“The results demonstrate, beyond any doubt, that the gap between official and real-world PHEV energy use and CO₂ output is much, much larger than for petrol or diesel cars,” the expert stated. “All regulatory adjustments regarding PHEVs should be implemented with extreme caution and in the light of that evidence.”