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Plug-in hybrid cars emit almost five times greater planet-heating emissions than official data show, according to a recent analysis.

Widening Discrepancy In Official and Actual CO2 Output

Statistics shows that PHEVs release just one-fifth lower CO₂ than conventional gas and diesel cars, based on analysis carried out by a non-profit organization. That differs sharply with laboratory estimates, which assumed a three-quarters decrease in emissions.

Analysts examined data from onboard fuel consumption monitors of 800,000 cars sold in Europe between 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab estimates, increased from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported figures are falling,” said a lead researcher involved in the study. “That gap is growing and poses a significant problem. Consequently, PHEVs emit almost as heavily as petrol vehicles.”

Key Reasons Behind the Discrepancy

Analysts attributed most of the gap to overestimates of the “utility factor” – the percentage of kilometers driven in battery mode relative to total distance. The team determined that just a quarter of driving was completed in electric mode, while lab assumptions assumed 84%.

Additionally, when running in electric mode, pollution levels were significantly higher than official projections. This happened because EV motors were not strong sufficient to function independently, resulting to combustion motors using fossil fuels for nearly one-third of the distance covered in EV mode.

Policy and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output allowed four large automaker companies to avoid more than €5bn in penalties between 2021 and 2023, by artificially easing adherence with EU average fleet CO₂ standards.

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

“The strong statements that automakers like to make about their PHEV vehicles are obviously far from the mark,” stated a automotive expert. “Buyers are being misled into believing that by buying a PHEV, they are helping the environment and saving costs. Actually, PHEVs are only slightly better than regular gas and diesel cars in terms of fuel consumption, CO₂ emissions, and running costs.”

Policy Debate and Industry Pressure

Hybrid cars have recently been drawn back into policy debates as automakers have pressed the EU to relax CO₂ targets. A planned ban on sales of new combustion engine cars in 2035 has faced intense pressure from the automotive sector and opposition from member states with significant automotive industries.

Some senior officials have suggested plug-in hybrids as a potential “flexibility” option to introduce in the legislation.

One independent energy policy specialist, who was unaffiliated with the research, described the report a “very useful addition” after years in which segments of the automotive sector claimed there was too little information to accurately assess real-world emissions.

“The results show, beyond any doubt, that the difference in official and real-world PHEV energy use and CO₂ output is significantly larger than for petrol or conventional cars,” the expert said. “Any policy adjustments concerning PHEVs should be implemented with utmost caution and in the light of that evidence.”