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

PHEVs emit nearly 5x more planet-heating emissions than official data indicate, according to a recent report.

Growing Gap In Official and Actual Emissions

Data shows that PHEVs emit only 19% lower CO₂ than traditional gas and diesel vehicles, based on research carried out by a non-profit group. That contrasts significantly with laboratory tests, which suggested a three-quarters reduction in pollution.

Analysts examined data from onboard fuel consumption meters of eight hundred thousand cars registered in the EU between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab estimates, up from 3.5 times in 2021.

“Actual emissions are increasing, while lab-reported emissions are decreasing,” said a lead researcher involved in the report. “That discrepancy is growing and poses a significant problem. Consequently, PHEVs pollute nearly as much as petrol cars.”

Key Reasons Driving the Emissions Gap

Researchers attributed the majority of the gap to overestimates of the “electric driving share” – the percentage of kilometers driven in battery power relative to total distance. They determined that just 27% of driving was done in electric mode, whereas official estimates assumed over four-fifths.

Additionally, when operating in electric mode, emission amounts were significantly higher than official estimates. That happened because electric motors were not strong enough to operate alone, resulting to combustion motors using fossil fuels for nearly a third of the distance covered in electric mode.

Regulatory and Financial Consequences

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

Additionally, owners of PHEVs would spend approximately €500 extra annually in operating expenses than would be estimated under lab tests.

“The strong claims that manufacturers often promote about their PHEV vehicles are obviously far from the truth,” commented a transport analyst. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the planet and saving money. Actually, PHEVs are little better than regular gas and diesel cars in terms of energy consumption, CO₂ emissions, and operating expenses.”

Political Debate and Industry Pressure

Hybrid cars have recently been drawn again into political debates as automakers have pressed the European Union to weaken CO₂ targets. A planned ban on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the car sector and opposition from member states with significant automotive industries.

Several high-level politicians have proposed plug-in hybrids as a possible “flexibility” solution to introduce in the legislation.

One independent energy policy specialist, who was unaffiliated with the study, described the analysis a “highly valuable addition” after a long period in which segments of the car industry argued there was too little data to properly evaluate real-world CO2 output.

“These findings show, without question, that the difference between official and real-world PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or diesel cars,” the expert said. “Any regulatory changes concerning PHEVs should be implemented with utmost caution and in the light of that data.”