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Plug-in hybrid cars emit almost 5x greater global warming pollution than official figures show, according to a new report.

Widening Discrepancy Between Official and Real-World CO2 Output

Statistics reveals that PHEVs release only one-fifth lower CO₂ than traditional petrol and diesel cars, according to research conducted by a advocacy organization. This differs sharply with laboratory estimates, which assumed a three-quarters reduction in pollution.

Analysts examined information from in-vehicle fuel consumption meters of eight hundred thousand vehicles sold in the EU between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, increased from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are falling,” said a senior analyst involved in the study. “This discrepancy is widening and creates a serious issue. As a result, PHEVs emit nearly as much as petrol cars.”

Primary Reasons Behind the Emissions Gap

Analysts attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of miles travelled in battery mode relative to overall distance. The team determined that only a quarter of driving was done in electric mode, while lab assumptions suggested 84%.

Even, when running in EV mode, pollution amounts were significantly higher than lab projections. That occurred because electric motors were insufficiently powerful enough to operate alone, leading to engines using gasoline for almost one-third of the distance completed in EV mode.

Regulatory and Financial Implications

According to estimates, the underestimation of PHEV emissions allowed several major carmaker companies to avoid more than €5bn in fines between 2021 and 2023, by artificially easing adherence with EU average fleet CO₂ standards.

Additionally, drivers of PHEVs would pay approximately €500 more annually in operating expenses than is assumed under lab conditions.

“The strong statements that manufacturers often promote about their plug-in hybrid vehicles are obviously way off the mark,” commented a transport expert. “Consumers are being misled into thinking that by buying a PHEV, they are helping the planet and cutting money. In reality, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating costs.”

Policy Debate and Automotive Pressure

Plug-in hybrid vehicles have recently been drawn back into policy debates as automakers have lobbied the EU to weaken CO₂ targets. A planned prohibition on new internal combustion vehicles in 2035 has faced intense pressure from the car industry and opposition from EU countries with significant car industries.

Several high-level politicians have proposed PHEVs as a possible “flexibility” solution to introduce in the regulation.

One external energy economics expert, who was unaffiliated with the study, described the report a “very useful contribution” after a long period in which parts of the automotive sector argued there was too little data to accurately evaluate actual emissions.

“The results demonstrate, without question, that the gap in lab and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for petrol or conventional cars,” they said. “All policy adjustments concerning PHEVs should be made with utmost care and in the light of that data.”