Plug-in Hybrid Cars Pollute Nearly as Heavily as Petrol Cars, Study Finds

PHEVs produce nearly 5x more planet-heating emissions than official figures show, according to a new analysis.

Widening Gap Between Lab and Actual Emissions

Data shows that PHEVs release only 19% less CO₂ than traditional gas and diesel vehicles, based on analysis carried out by a non-profit organization. This contrasts significantly with laboratory estimates, which assumed a three-quarters reduction in emissions.

Researchers examined data from onboard fuel consumption monitors of 800,000 vehicles sold in the EU between 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, increased from three and a half times in 2021.

“Actual emissions are rising, while official figures are decreasing,” stated a lead researcher participating in the report. “That discrepancy is widening and creates a significant issue. As a result, PHEVs emit nearly as much as petrol vehicles.”

Primary Reasons Behind the Emissions Gap

Analysts attributed most of the difference to overestimates of the “utility factor” – the ratio of miles travelled in electric power relative to total mileage. The team found that only 27% of driving was completed in electric mode, whereas lab estimates suggested 84%.

Even, when operating in EV mode, emission amounts were well above lab estimates. This happened because electric motors were insufficiently powerful sufficient to function independently, resulting to combustion motors using gasoline for nearly one-third of the travel covered in EV mode.

Regulatory and Financial Consequences

According to estimates, the lowballing of PHEV emissions allowed four large carmaker companies to escape over €5bn in fines from 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ standards.

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

“The strong claims that automakers often promote about their plug-in hybrid vehicles are obviously way off the mark,” stated a automotive expert. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are little improved than regular petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and running expenses.”

Political Debate and Industry Lobbying

Hybrid vehicles have recently been drawn back into political discussions as carmakers have lobbied the EU to weaken CO₂ targets. A proposed ban on new internal combustion cars in 2035 has faced intense lobbying from the automotive sector and opposition from member states with large car industries.

Several senior officials have suggested PHEVs as a potential “flexibility” solution to introduce in the legislation.

An external energy policy expert, who was not involved with the research, described the analysis a “very useful addition” after years in which parts of the car industry claimed there was insufficient information to properly evaluate real-world emissions.

“These findings demonstrate, beyond any doubt, that the difference in lab and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or conventional cars,” the expert said. “Any regulatory changes regarding PHEVs should be made with utmost caution and considering that evidence.”