🔗 Share this article

Plug-in hybrid electric vehicles release nearly 5x more global warming emissions than lab-reported figures show, according to a new report.

Widening Discrepancy In Official and Actual CO2 Output

Data shows that PHEVs emit only one-fifth lower CO₂ than traditional petrol and diesel cars, according to analysis conducted by a non-profit organization. This contrasts significantly with lab estimates, which suggested a three-quarters decrease in pollution.

Analysts examined information from onboard fuel consumption monitors of 800,000 cars sold in the EU from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, increased from three and a half times in 2021.

“Actual CO2 output are rising, while official figures are falling,” said a senior analyst involved in the report. “That gap is growing and poses a serious issue. Consequently, PHEVs pollute almost as much as gasoline vehicles.”

Key Factors Driving the Emissions Gap

Researchers attributed most of the difference to overestimates of the “electric driving share” – the percentage of kilometers driven in electric power compared to total mileage. The team determined that just a quarter of travel was done in electric mode, while official estimates suggested over four-fifths.

Additionally, when running in electric mode, pollution levels were well above official estimates. This happened because electric motors were not strong enough to operate independently, resulting to engines burning fossil fuels for almost a third of the distance covered in electric mode.

Regulatory and Financial Consequences

According to estimates, the underestimation of PHEV emissions enabled four major carmaker groups to avoid more than €5bn in fines from 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs could pay about €500 extra annually in operating expenses than is estimated under laboratory tests.

“The strong claims that manufacturers often promote about their plug-in hybrid cars are obviously way off the mark,” commented a transport expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are helping the planet and saving money. Actually, PHEVs are little better than standard petrol and diesel cars in terms of energy consumption, CO₂ emissions, and running costs.”

Political Debate and Automotive Pressure

Hybrid cars have recently been drawn again into policy debates as automakers have lobbied the EU to relax CO₂ standards. A planned prohibition on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the automotive industry and opposition from EU countries with large car industries.

Some high-level politicians have proposed plug-in hybrids as a possible “compromise” option to introduce in the legislation.

One independent energy policy expert, who was not involved with the study, described the analysis a “very useful contribution” after years in which parts of the automotive industry claimed there was too little information to accurately assess actual CO2 output.

“These findings demonstrate, beyond any doubt, that the difference in lab and actual PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or diesel vehicles,” the expert said. “Any policy adjustments regarding PHEVs should be implemented with utmost caution and considering this data.”