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Plug-in hybrid cars release nearly 5x more planet-heating emissions than official figures indicate, according to a recent analysis.

Growing Gap In Lab and Real-World CO2 Output

Data shows that PHEVs release just one-fifth less CO₂ than traditional gas and diesel cars, based on analysis carried out by a non-profit group. That differs sharply with laboratory estimates, which suggested a three-quarters reduction in pollution.

Researchers studied information from onboard fuel consumption meters of eight hundred thousand vehicles sold in the EU from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, increased from 3.5 times in 2021.

“Actual emissions are rising, while official emissions are falling,” stated a senior analyst involved in the study. “That gap is growing and poses a significant issue. Consequently, PHEVs emit almost as heavily as gasoline cars.”

Primary Reasons Behind the Emissions Gap

Analysts attributed the majority of the difference to inflated estimates of the “utility factor” – the percentage of kilometers driven in electric power compared to overall mileage. They found that just a quarter of travel was done in EV mode, whereas lab estimates assumed over four-fifths.

Even, when running in EV mode, pollution amounts were significantly higher than lab projections. That happened because EV motors were insufficiently powerful enough to operate independently, resulting to engines burning fossil fuels for nearly a third of the distance covered in EV mode.

Regulatory and Financial Implications

Based on calculations, the underestimation of PHEV CO2 output allowed several large carmaker groups to avoid over €5bn in fines from 2021 and 2023, by falsely easing adherence with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would spend about €500 more per year in operating expenses than is estimated under laboratory tests.

“The bold statements that automakers often promote about their PHEV vehicles are clearly way off the truth,” stated a transport expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the environment and saving costs. Actually, PHEVs are little improved than standard petrol and diesel vehicles in terms of energy use, CO₂ production, and running costs.”

Political Discussion and Automotive Lobbying

Hybrid vehicles have lately been brought again into political debates as automakers have pressed the EU to weaken CO₂ standards. A proposed ban on new internal combustion vehicles in 2035 has faced heavy lobbying from the car sector and resistance from EU countries with large automotive manufacturing.

Some senior officials have proposed PHEVs as a possible “flexibility” option to include in the regulation.

One independent energy economics specialist, who was unaffiliated with the research, described the report a “very useful contribution” after years in which segments of the automotive sector claimed there was insufficient data to accurately assess real-world emissions.

“The results demonstrate, beyond any doubt, that the difference between lab and real-world PHEV energy use and CO₂ output is significantly larger than for petrol or diesel cars,” the expert said. “Any policy adjustments regarding PHEVs should be implemented with utmost caution and in the light of this data.”