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

Widening Discrepancy Between Official and Real-World CO2 Output

Statistics shows that PHEVs release only one-fifth lower CO₂ than conventional gas and diesel cars, according to research conducted by a advocacy organization. That differs significantly with laboratory tests, which assumed a three-quarters reduction in pollution.

Researchers examined information from onboard fuel consumption meters of 800,000 cars sold in the EU from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab figures, up from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are decreasing,” stated a senior analyst involved in the report. “That gap is growing and poses a serious problem. Consequently, PHEVs emit nearly as much as gasoline cars.”

Primary Reasons Behind the Discrepancy

Researchers linked most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in battery power relative to overall mileage. They determined that just 27% of travel was done in EV mode, whereas lab estimates suggested over four-fifths.

Additionally, when running in EV mode, pollution levels were significantly higher than official projections. This happened because electric motors were not strong enough to operate independently, leading to combustion motors using gasoline for nearly a third of the distance completed in EV mode.

Policy and Economic Implications

According to estimates, the underestimation of PHEV emissions allowed several large carmaker companies to avoid over €5bn in penalties between 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ targets.

Furthermore, drivers of PHEVs could spend about €500 extra annually in operating costs than would be estimated under lab conditions.

“The bold claims that manufacturers often promote about their plug-in hybrid cars are obviously way off the truth,” commented a transport analyst. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of energy consumption, CO₂ production, and operating costs.”

Political Discussion and Automotive Lobbying

Hybrid vehicles have recently been drawn again into policy discussions as automakers have pressed the European Union to relax CO₂ targets. A planned prohibition on sales of new internal combustion cars in 2035 has faced heavy pressure from the car sector and resistance from member states with large car industries.

Several senior politicians have proposed PHEVs as a potential “flexibility” option to introduce in the legislation.

One external energy policy specialist, who was not involved with the study, called the analysis a “highly valuable addition” after years in which segments of the car industry claimed there was insufficient information to accurately evaluate actual CO2 output.

“These findings demonstrate, without question, that the gap between official and actual PHEV fuel consumption and CO₂ output is much, much greater than for gasoline or conventional cars,” the expert said. “Any policy changes concerning PHEVs should be implemented with extreme care and considering that evidence.”