Plug-in Hybrid electric Cars Emit Almost as Much as Gasoline Vehicles, Study Finds

Plug-in hybrid cars release nearly five times greater planet-heating pollution than official data show, as per a new analysis.

Widening Gap Between Lab and Actual Emissions

Data reveals that PHEVs emit just one-fifth lower CO₂ than traditional petrol and diesel vehicles, according to research carried out by a non-profit organization. This differs sharply with laboratory tests, which assumed a 75% reduction in emissions.

Analysts studied data from onboard energy use monitors 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 greater than official figures, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are falling,” stated a lead researcher participating in the study. “This discrepancy is widening and poses a serious problem. Consequently, PHEVs pollute nearly as much as petrol vehicles.”

Primary Factors Driving the Emissions Gap

Researchers linked most of the difference to overestimates of the “utility factor” – the percentage of kilometers driven in electric mode relative to total mileage. They found that just 27% of driving was completed in EV mode, while official assumptions suggested over four-fifths.

Additionally, when running in electric mode, pollution amounts were well above official projections. That occurred because EV motors were not strong sufficient to function alone, leading to engines using fossil fuels for nearly a third of the distance completed in electric mode.

Regulatory and Economic Consequences

Based on estimates, the underestimation of PHEV CO2 output enabled four large automaker groups to escape more than €5bn in fines from 2021 and 2023, by falsely simplifying compliance with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs could pay approximately €500 extra annually in operating expenses than is estimated under lab conditions.

“The strong statements that manufacturers often promote about their plug-in hybrid vehicles are obviously far from the mark,” commented a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are little improved than regular petrol and diesel vehicles in terms of energy use, CO₂ emissions, and operating costs.”

Political Debate and Automotive Lobbying

Plug-in hybrid vehicles have recently been drawn again into policy debates as automakers have pressed the EU to relax CO₂ standards. A proposed ban on sales of new internal combustion cars in 2035 has faced heavy pressure from the car industry and resistance from member states with significant car industries.

Some high-level officials have proposed plug-in hybrids as a possible “compromise” solution to include in the legislation.

An independent energy policy expert, who was not involved with the study, described the report a “very useful contribution” after years in which parts of the automotive industry claimed there was too little information to accurately evaluate actual emissions.

“The results demonstrate, without question, that the gap in lab and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or diesel vehicles,” the expert said. “All policy changes concerning PHEVs should be implemented with utmost care and considering this data.”