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PHEVs emit almost 5x greater planet-heating pollution than official data show, according to a new report.

Growing Gap Between Lab and Real-World CO2 Output

Statistics reveals that PHEVs emit just one-fifth less CO₂ than conventional gas and diesel cars, based on research carried out by a non-profit group. This differs significantly with laboratory estimates, which suggested a three-quarters reduction in emissions.

Analysts studied information from onboard energy use monitors of 800,000 cars registered in the EU from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, increased from 3.5 times in 2021.

“Actual emissions are rising, while official emissions are falling,” stated a lead researcher involved in the report. “This gap is growing and creates a significant issue. Consequently, PHEVs emit nearly as heavily as gasoline cars.”

Key Reasons Behind the Emissions Gap

Analysts linked the majority of the gap to overestimates of the “electric driving share” – the ratio of miles driven in electric mode relative to overall mileage. The team found that only 27% of driving was done in EV mode, whereas official estimates assumed over four-fifths.

Additionally, when running in electric mode, pollution levels were well above official estimates. That happened because electric motors were insufficiently powerful enough to operate alone, resulting to combustion motors burning gasoline for nearly a third of the distance completed in electric mode.

Policy and Economic Implications

Based on estimates, the lowballing of PHEV CO2 output enabled four major automaker groups to avoid more than €5bn in fines between 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would spend approximately €500 more annually in running costs than would be estimated under laboratory conditions.

“The strong claims that manufacturers often promote about their plug-in hybrid cars are obviously way off the truth,” commented a transport expert. “Consumers are being duped into believing that by buying a PHEV, they are helping the planet and saving money. Actually, PHEVs are little improved than regular gas and diesel vehicles in terms of energy use, CO₂ emissions, and operating costs.”

Policy Debate and Industry Pressure

Plug-in hybrid vehicles have recently been drawn again into policy discussions as automakers have lobbied the EU to relax CO₂ targets. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced intense pressure from the car industry and resistance from member states with large car industries.

Several senior officials have proposed plug-in hybrids as a possible “flexibility” option to include in the regulation.

An independent energy policy specialist, who was not involved with the study, described the analysis a “very useful addition” after a long period in which segments of the automotive sector claimed there was too little information to accurately evaluate real-world emissions.

“These findings show, without question, that the gap in official and actual PHEV energy use and CO₂ emissions is significantly larger than for gasoline or diesel vehicles,” the expert said. “All policy adjustments regarding PHEVs should be made with utmost caution and considering that evidence.”