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Plug-in hybrid electric vehicles emit nearly five times greater planet-heating emissions than official data indicate, according to a new analysis.

Growing Gap In Official and Real-World Emissions

Statistics reveals that PHEVs release just one-fifth less CO₂ than traditional petrol and diesel vehicles, based on research carried out by a non-profit organization. That contrasts sharply with lab estimates, which assumed a three-quarters reduction in emissions.

Analysts examined information from in-vehicle energy use meters of 800,000 cars registered in Europe between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, increased from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are falling,” said a senior analyst participating in the study. “This gap is widening and creates a significant problem. As a result, PHEVs emit almost as much as petrol vehicles.”

Primary Reasons Driving the Emissions Gap

Analysts linked most of the gap to inflated estimates of the “electric driving share” – the percentage of miles travelled in electric mode relative to overall distance. The team determined that only a quarter of driving was completed in EV mode, while official estimates suggested 84%.

Additionally, when running in electric mode, emission levels were significantly higher than lab estimates. This happened because EV motors were insufficiently powerful enough to function alone, leading to combustion motors using gasoline for almost one-third of the travel covered in EV mode.

Regulatory and Economic Implications

Based on estimates, the lowballing of PHEV emissions enabled several major carmaker companies to escape over €5bn in fines from 2021 and 2023, by falsely easing compliance with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs could pay about €500 more per year in running expenses than would be estimated under lab tests.

“The strong statements that manufacturers often promote about their plug-in hybrid vehicles are clearly far from the mark,” stated a automotive expert. “Consumers are being misled into thinking that by buying a PHEV, they are helping the planet and saving money. Actually, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating expenses.”

Political Discussion and Industry Pressure

Hybrid vehicles have lately been drawn back into political debates as automakers have pressed the EU to weaken CO₂ standards. A proposed prohibition on sales of new internal combustion cars in 2035 has faced intense lobbying from the automotive industry and opposition from EU countries with large car manufacturing.

Some senior politicians have proposed plug-in hybrids as a possible “compromise” option to introduce in the legislation.

One external energy policy expert, who was not involved with the study, described the report a “highly valuable contribution” after a long period in which segments of the automotive sector argued there was too little data to properly evaluate actual emissions.

“These findings show, without question, that the gap in lab and actual PHEV energy use and CO₂ output is much, much greater than for gasoline or diesel cars,” they stated. “All regulatory adjustments concerning PHEVs should be implemented with utmost caution and in the light of this data.”