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Plug-in hybrid electric vehicles produce almost 5x greater planet-heating pollution than lab-reported data show, according to a recent report.

Widening Gap In Official and Real-World Emissions

Statistics reveals that PHEVs release just one-fifth lower CO₂ than conventional petrol and diesel cars, according to analysis conducted by a non-profit group. That contrasts sharply with laboratory tests, which suggested a 75% reduction in pollution.

Analysts examined information from in-vehicle energy use meters of 800,000 cars sold in Europe from 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab estimates, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while official figures are decreasing,” stated a senior researcher participating in the report. “This discrepancy is growing and creates a serious issue. Consequently, PHEVs emit nearly as much as gasoline cars.”

Key Factors Driving the Emissions Gap

Researchers attributed most of the difference to inflated estimates of the “utility factor” – the percentage of miles driven in electric power compared to overall mileage. They determined that just 27% of driving was done in EV mode, whereas lab assumptions assumed over four-fifths.

Even, when running in EV mode, pollution levels were well above lab estimates. That happened because EV motors were insufficiently powerful enough to operate alone, resulting to combustion motors using fossil fuels for almost one-third of the travel completed in electric mode.

Policy and Financial Consequences

According to calculations, the lowballing of PHEV emissions enabled several large automaker groups to avoid over €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ targets.

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

“The strong claims that manufacturers often promote about their plug-in hybrid cars are clearly far from the mark,” commented a transport expert. “Buyers are being duped into believing that by buying a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are only slightly improved than regular petrol and diesel vehicles in terms of energy use, CO₂ emissions, and running costs.”

Political Debate and Industry Pressure

Hybrid vehicles have recently been drawn again into policy discussions as carmakers have pressed the European Union to weaken CO₂ standards. A planned ban on sales of new combustion engine cars in 2035 has faced intense lobbying from the car sector and resistance from EU countries with large car industries.

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

One external energy policy expert, who was unaffiliated with the research, called the report a “highly valuable contribution” after years in which segments of the car sector argued there was insufficient data to properly evaluate real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the difference between lab and real-world PHEV energy use and CO₂ emissions is much, much greater than for gasoline or conventional vehicles,” the expert stated. “All policy changes regarding PHEVs should be implemented with utmost caution and considering that data.”