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Plug-in hybrid cars release nearly 5x more global warming emissions than official figures indicate, according to a new report.

Growing Discrepancy In Lab and Real-World CO2 Output

Statistics shows that PHEVs emit just one-fifth lower CO₂ than conventional gas and diesel cars, according to analysis conducted by a advocacy group. That contrasts sharply with laboratory tests, which suggested a 75% decrease in emissions.

Analysts examined data from in-vehicle energy use meters of eight hundred thousand vehicles sold in Europe from 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official estimates, up from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported figures are falling,” stated a senior researcher involved in the report. “This discrepancy is growing and poses a significant issue. Consequently, PHEVs pollute almost as heavily as petrol cars.”

Primary Factors Driving the Discrepancy

Analysts attributed most of the difference to inflated estimates of the “electric driving share” – the percentage of miles travelled in battery mode relative to total mileage. The team found that only 27% of travel was completed in EV mode, while lab estimates suggested over four-fifths.

Additionally, when operating in electric mode, pollution levels were significantly higher than official estimates. This happened because EV motors were insufficiently powerful enough to function independently, resulting to engines burning gasoline for almost one-third of the distance covered in electric mode.

Policy and Financial Consequences

Based on calculations, the lowballing of PHEV CO2 output allowed several large automaker companies to escape over €5bn in fines from 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs would spend approximately €500 more annually in running costs than is assumed under laboratory conditions.

“The strong claims that manufacturers like to make about their plug-in hybrid vehicles are clearly way off the truth,” stated a transport analyst. “Buyers are being duped into thinking that by buying a PHEV, they are helping the planet and cutting money. In reality, PHEVs are only slightly improved than regular petrol and diesel cars in terms of energy consumption, CO₂ emissions, and operating expenses.”

Policy Debate and Industry Lobbying

Plug-in hybrid vehicles have recently been drawn again into policy debates as automakers have pressed the European Union to weaken CO₂ targets. A planned ban on new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive sector and resistance from member states with large car industries.

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

One external energy policy expert, who was unaffiliated with the study, called the analysis a “highly valuable contribution” after a long period in which segments of the car sector argued there was insufficient data to accurately assess real-world CO2 output.

“These findings show, beyond any doubt, that the gap in lab and actual PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or diesel cars,” the expert said. “Any regulatory adjustments concerning PHEVs should be made with utmost care and considering that evidence.”