Plug in Hybrid Vehicles Emit Almost as Much as Petrol Vehicles, Study Finds

Plug-in hybrid cars release nearly 5x more global warming pollution than lab-reported figures indicate, according to a new analysis.

Growing Gap Between Official and Real-World CO2 Output

Statistics reveals that PHEVs release only 19% less CO₂ than traditional gas and diesel cars, based on research carried out by a non-profit group. This differs significantly with lab tests, which assumed a three-quarters decrease in emissions.

Analysts examined data from onboard energy use monitors of 800,000 cars registered in Europe from 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported figures are decreasing,” said a lead researcher participating in the report. “That gap is growing and poses a serious problem. As a result, PHEVs emit almost as heavily as petrol cars.”

Primary Factors Behind the Emissions Gap

Analysts attributed most of the difference to inflated estimates of the “utility factor” – the ratio of miles driven in electric mode compared to overall mileage. The team found that only 27% of driving was done in electric mode, whereas lab assumptions suggested 84%.

Even, when operating in electric mode, emission amounts were significantly higher than official projections. This occurred because electric motors were not strong sufficient to function independently, resulting to engines burning gasoline for nearly a third of the travel completed in EV mode.

Regulatory and Economic Implications

Based on calculations, the lowballing of PHEV CO2 output enabled four large automaker groups to avoid over €5bn in fines between 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs would spend about €500 more annually in running expenses than would be assumed under laboratory conditions.

“The bold statements that automakers often promote about their plug-in hybrid cars are obviously far from the truth,” stated a transport expert. “Buyers are being duped into believing that by purchasing a PHEV, they are helping the environment and cutting money. Actually, PHEVs are little better than standard gas and diesel cars in terms of energy use, CO₂ production, and running expenses.”

Political Discussion and Industry Lobbying

Plug-in hybrid vehicles have recently been brought again into policy debates as automakers have pressed the European Union to relax CO₂ targets. A planned prohibition on sales of new combustion engine cars in 2035 has faced intense lobbying from the car sector and opposition from EU countries with large automotive manufacturing.

Some high-level politicians have suggested PHEVs as a possible “compromise” option to introduce in the legislation.

An external energy economics specialist, who was not involved with the study, described the analysis a “very useful contribution” after a long period in which parts of the automotive industry argued there was too little data to accurately evaluate real-world CO2 output.

“These findings demonstrate, without question, that the gap between official and actual PHEV energy use and CO₂ emissions is significantly larger than for gasoline or diesel vehicles,” they stated. “Any policy adjustments concerning PHEVs should be implemented with extreme care and in the light of that evidence.”