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Plug-in hybrid cars produce nearly five times greater global warming emissions than official figures indicate, as per a new report.

Widening Discrepancy In Official and Real-World CO2 Output

Statistics shows that PHEVs emit only one-fifth lower CO₂ than traditional gas and diesel vehicles, according to analysis conducted by a non-profit group. That contrasts significantly with laboratory tests, which suggested a three-quarters decrease in emissions.

Analysts examined data from in-vehicle fuel consumption monitors of eight hundred thousand vehicles registered in Europe between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab estimates, up from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported figures are decreasing,” stated a senior analyst involved in the report. “This discrepancy is growing and creates a significant issue. Consequently, PHEVs emit almost as much as petrol cars.”

Key Factors Behind the Discrepancy

Analysts linked the majority of the difference to overestimates of the “utility factor” – the ratio of kilometers driven in battery mode relative to total mileage. They determined that only a quarter of travel was completed in EV mode, whereas official assumptions assumed 84%.

Additionally, when running in EV mode, pollution levels were well above official estimates. This happened because electric motors were insufficiently powerful sufficient to function alone, leading to combustion motors burning gasoline for almost a third of the travel completed in EV mode.

Regulatory and Financial Consequences

According to estimates, the lowballing of PHEV CO2 output allowed four major carmaker companies to escape over €5bn in penalties between 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ targets.

Furthermore, owners of PHEVs would spend about €500 more annually in operating costs than would be estimated under laboratory conditions.

“The strong claims that manufacturers like to make about their plug-in hybrid vehicles are clearly way off the mark,” stated a transport analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the environment and saving money. In reality, PHEVs are only slightly better than standard petrol and diesel cars in terms of fuel use, CO₂ emissions, and running expenses.”

Policy Discussion and Automotive Pressure

Plug-in hybrid vehicles have lately been drawn again into political discussions as carmakers have pressed the EU to weaken CO₂ targets. A proposed ban on new internal combustion vehicles in 2035 has faced intense pressure from the car industry and resistance from EU countries with significant automotive industries.

Some high-level officials have suggested plug-in hybrids as a potential “compromise” solution to include in the regulation.

One independent energy economics specialist, who was unaffiliated with the study, described the report a “very useful contribution” after years in which segments of the car industry argued there was insufficient data to accurately assess real-world emissions.

“The results demonstrate, beyond any doubt, that the difference in lab and actual PHEV energy use and CO₂ emissions is significantly greater than for petrol or conventional cars,” they said. “Any regulatory adjustments regarding PHEVs should be made with extreme care and in the light of that evidence.”