Plug in Hybrid Vehicles Emit Nearly as Heavily as Gasoline Cars, Report Finds

Plug-in hybrid cars release almost five times greater global warming emissions than lab-reported figures indicate, according to a new analysis.

Growing Gap Between Lab and Real-World CO2 Output

Data shows that PHEVs emit only 19% lower CO₂ than conventional petrol and diesel cars, according to analysis carried out by a advocacy organization. This contrasts significantly with laboratory estimates, which suggested a three-quarters reduction in pollution.

Analysts studied information from in-vehicle fuel consumption monitors of 800,000 cars registered in Europe between 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, up from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported emissions are falling,” said a lead analyst participating in the report. “This gap is growing and creates a significant problem. As a result, PHEVs pollute nearly as heavily as gasoline vehicles.”

Key Factors Behind the Emissions Gap

Researchers linked most of the gap to inflated estimates of the “utility factor” – the ratio of kilometers travelled in electric mode compared to total mileage. The team found that just a quarter of travel was completed in EV mode, while official estimates suggested 84%.

Additionally, when operating in EV mode, emission amounts were well above lab estimates. This happened because electric motors were insufficiently powerful enough to operate independently, resulting to combustion motors burning gasoline for nearly a third of the travel completed in EV mode.

Regulatory and Economic Consequences

According to calculations, the underestimation of PHEV emissions allowed several large carmaker groups to escape more than €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ standards.

Additionally, owners of PHEVs could spend about €500 more per year in running expenses than is assumed under lab conditions.

“The strong claims that automakers like to make about their PHEV vehicles are clearly way off the truth,” stated a transport analyst. “Consumers are being duped into believing that by buying a PHEV, they are helping the planet and cutting costs. In reality, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of energy use, CO₂ emissions, and operating expenses.”

Political Debate and Automotive Pressure

Plug-in hybrid vehicles have lately been drawn back into policy debates as carmakers have pressed the EU to relax CO₂ standards. A proposed ban on new internal combustion vehicles in 2035 has faced intense pressure from the car sector and opposition from member states with large automotive manufacturing.

Some senior politicians have proposed plug-in hybrids as a potential “flexibility” solution to include in the legislation.

An external energy policy specialist, who was not involved with the research, called the analysis a “highly valuable contribution” after a long period in which segments of the automotive industry argued there was insufficient data to properly evaluate actual CO2 output.

“These findings show, beyond any doubt, that the gap in official and real-world PHEV energy use and CO₂ output is significantly larger than for gasoline or diesel cars,” the expert said. “All regulatory adjustments concerning PHEVs should be implemented with utmost caution and considering that data.”