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PHEVs release almost five times more planet-heating pollution than official figures indicate, as per a recent report.

Widening Gap Between Official and Real-World Emissions

Statistics shows that PHEVs release only 19% less CO₂ than conventional gas and diesel vehicles, based on research carried out by a advocacy organization. This contrasts sharply with laboratory tests, which suggested a 75% reduction in pollution.

Researchers examined data from in-vehicle energy use monitors of 800,000 vehicles registered in Europe from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, increased from three and a half times in 2021.

“Actual emissions are rising, while official emissions are falling,” stated a lead researcher participating in the study. “That discrepancy is widening and poses a significant issue. Consequently, PHEVs emit nearly as much as petrol vehicles.”

Key Reasons Driving the Emissions Gap

Analysts attributed most of the difference to overestimates of the “utility factor” – the ratio of kilometers travelled in electric mode compared to overall mileage. The team determined that only 27% of driving was completed in electric mode, whereas official estimates assumed over four-fifths.

Even, when operating in electric mode, pollution amounts were significantly higher than lab estimates. This happened because electric motors were insufficiently powerful enough to operate independently, leading to combustion motors burning gasoline for almost a third of the distance completed in electric mode.

Policy and Economic Consequences

Based on calculations, the underestimation of PHEV CO2 output enabled several large automaker groups to avoid over €5bn in penalties between 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ targets.

Additionally, owners of PHEVs would pay about €500 more annually in running costs than would be assumed under lab tests.

“The strong statements that automakers like to make about their PHEV vehicles are obviously far from the truth,” commented a transport analyst. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are only slightly better than regular petrol and diesel cars in terms of energy use, CO₂ production, and operating costs.”

Policy Discussion and Automotive Pressure

Plug-in hybrid cars have recently been drawn again into policy debates as carmakers have lobbied the EU to relax CO₂ targets. A proposed prohibition on new combustion engine cars in 2035 has faced heavy pressure from the automotive sector and opposition from EU countries with significant automotive manufacturing.

Some high-level politicians have proposed PHEVs as a potential “compromise” solution to introduce in the regulation.

One external energy policy expert, who was unaffiliated with the research, described the report a “very useful contribution” after years in which segments of the car sector argued there was insufficient data to properly evaluate actual CO2 output.

“The results demonstrate, without question, that the gap in official and real-world PHEV energy use and CO₂ emissions is much, much larger than for gasoline or diesel cars,” they stated. “All policy adjustments concerning PHEVs should be implemented with extreme care and in the light of this data.”