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Plug-in hybrid electric vehicles produce almost 5x greater global warming pollution than lab-reported figures show, as per a new report.

Growing Gap In Official and Real-World CO2 Output

Data reveals that PHEVs release just one-fifth lower CO₂ than conventional petrol and diesel cars, according to analysis conducted by a non-profit organization. This contrasts significantly with lab estimates, which suggested a 75% reduction in emissions.

Researchers examined data from onboard energy use meters of 800,000 vehicles sold in the EU from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official emissions are decreasing,” stated a senior analyst involved in the report. “That gap is widening and creates a significant issue. As a result, PHEVs emit nearly as much as gasoline vehicles.”

Key Reasons Behind the Discrepancy

Analysts linked the majority of the gap to inflated estimates of the “electric driving share” – the ratio of miles driven in battery mode compared to total mileage. They determined that just 27% of driving was done in electric mode, while official assumptions suggested 84%.

Even, when running in EV mode, pollution levels were well above lab estimates. This occurred because electric motors were insufficiently powerful enough to function alone, resulting to combustion motors burning fossil fuels for almost a third of the travel covered in EV mode.

Regulatory and Financial Consequences

According to estimates, the underestimation of PHEV emissions enabled several large carmaker groups to escape more than €5bn in fines from 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs would spend about €500 extra annually in running expenses than is estimated under laboratory tests.

“The bold claims that manufacturers often promote about their plug-in hybrid cars are clearly far from the truth,” commented a transport expert. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are little improved than regular gas and diesel cars in terms of fuel consumption, CO₂ emissions, and operating costs.”

Political Debate and Automotive Pressure

Plug-in hybrid vehicles have lately been drawn back into policy debates as automakers have pressed the European Union to relax CO₂ standards. A proposed prohibition on sales of new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive industry and resistance from EU countries with large automotive industries.

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

An external energy policy specialist, who was not involved with the research, called the report a “highly valuable addition” after a long period in which segments of the car sector claimed there was insufficient data to properly evaluate real-world CO2 output.

“The results demonstrate, without question, that the gap between lab and actual PHEV energy use and CO₂ output is much, much larger than for petrol or diesel vehicles,” the expert said. “Any policy adjustments concerning PHEVs should be implemented with utmost caution and in the light of this data.”