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Plug-in hybrid electric vehicles emit almost five times greater planet-heating emissions than lab-reported data show, according to a new analysis.

Growing Gap Between Lab and Real-World CO2 Output

Statistics shows that PHEVs emit only one-fifth lower CO₂ than traditional petrol and diesel cars, based on research conducted by a advocacy organization. That contrasts sharply with lab estimates, which assumed a three-quarters decrease in pollution.

Researchers examined data from onboard fuel consumption meters of 800,000 cars sold in the EU between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, up from 3.5 times in 2021.

“Real-world CO2 output are rising, while official emissions are falling,” said a lead researcher involved in the study. “That discrepancy is growing and poses a significant issue. Consequently, PHEVs emit nearly as much as gasoline vehicles.”

Key Factors Behind the Discrepancy

Researchers linked the majority of the difference to inflated estimates of the “utility factor” – the percentage of miles driven in electric power compared to overall mileage. They determined that only a quarter of driving was completed in electric mode, whereas official assumptions suggested over four-fifths.

Even, when operating in EV mode, emission levels were well above official projections. That happened because electric motors were insufficiently powerful sufficient to function independently, resulting to combustion motors using gasoline for nearly a third of the distance completed in electric mode.

Policy and Economic Implications

Based on estimates, the lowballing of PHEV emissions allowed several large carmaker groups to escape more than €5bn in penalties from 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ standards.

Furthermore, drivers of PHEVs could spend about €500 more per year in running costs than is assumed under laboratory tests.

“The bold claims that automakers often promote about their plug-in hybrid cars are clearly way off the mark,” stated a automotive analyst. “Consumers are being misled into thinking that by buying a PHEV, they are helping the planet and cutting money. Actually, PHEVs are only slightly improved than standard gas and diesel cars in terms of fuel consumption, CO₂ emissions, and running costs.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid vehicles have recently been brought again into policy debates as carmakers have lobbied the EU to weaken CO₂ targets. A proposed prohibition on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the car industry and opposition from EU countries with significant car industries.

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

One external energy economics specialist, who was unaffiliated with the research, called the analysis a “highly valuable contribution” after a long period in which segments of the car sector argued there was insufficient information to properly evaluate real-world CO2 output.

“These findings show, beyond any doubt, that the gap in official and actual PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or diesel vehicles,” they stated. “All policy adjustments concerning PHEVs should be implemented with utmost caution and considering that data.”