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

Widening Discrepancy In Lab and Real-World CO2 Output

Data reveals that PHEVs release only one-fifth less CO₂ than traditional petrol and diesel vehicles, based on research carried out by a non-profit organization. That differs sharply with laboratory tests, which suggested a 75% reduction in emissions.

Researchers examined data from in-vehicle fuel consumption meters of eight hundred thousand vehicles sold in Europe between 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while official emissions are decreasing,” said a lead analyst participating in the report. “This discrepancy is growing and poses a significant issue. Consequently, PHEVs pollute nearly as much as gasoline vehicles.”

Key Factors Driving the Discrepancy

Researchers linked the majority of the gap to overestimates of the “utility factor” – the ratio of kilometers driven in battery power relative to overall distance. The team found that only 27% of driving was done in electric mode, while lab assumptions suggested 84%.

Even, when running in EV mode, emission levels were well above lab projections. That happened because EV motors were insufficiently powerful enough to function alone, leading to engines burning fossil fuels for nearly one-third of the distance completed in EV mode.

Regulatory and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output enabled several large automaker groups to avoid over €5bn in fines between 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs would spend about €500 more annually in operating costs than is estimated under laboratory tests.

“The bold claims that manufacturers like to make about their plug-in hybrid vehicles are obviously far from the truth,” stated a transport analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the planet and cutting costs. In reality, PHEVs are only slightly improved than regular gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Political Debate and Industry Lobbying

Plug-in hybrid vehicles have lately been drawn back into policy debates as automakers have pressed the EU to weaken CO₂ targets. A proposed ban on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the car industry and resistance from EU countries with large car manufacturing.

Several high-level officials have proposed PHEVs as a possible “compromise” solution to include in the regulation.

One external energy economics specialist, who was not involved with the study, called the report a “highly valuable addition” after years in which parts of the automotive industry claimed there was insufficient information to accurately assess real-world emissions.

“These findings show, beyond any doubt, that the difference in lab and real-world PHEV fuel consumption and CO₂ output is much, much larger than for petrol or conventional vehicles,” the expert stated. “Any regulatory adjustments regarding PHEVs should be made with extreme care and considering that data.”