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Plug-in hybrid cars release almost 5x greater planet-heating emissions than lab-reported figures show, according to a recent analysis.

Widening Discrepancy Between Lab and Real-World Emissions

Data shows that PHEVs emit just one-fifth lower CO₂ than traditional petrol and diesel vehicles, based on research conducted by a non-profit organization. That contrasts sharply with laboratory estimates, which suggested a three-quarters reduction in pollution.

Analysts studied data from onboard fuel consumption monitors of 800,000 cars sold in the EU between 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, up from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are falling,” stated a lead analyst participating in the study. “That gap is widening and creates a serious problem. As a result, PHEVs emit nearly as much as petrol cars.”

Primary Reasons Behind the Discrepancy

Researchers linked the majority of the gap to overestimates of the “utility factor” – the percentage of kilometers travelled in electric power compared to overall distance. The team found that just 27% of driving was completed in EV mode, whereas lab estimates assumed 84%.

Even, when operating in electric mode, emission amounts were well above official estimates. That happened because electric motors were insufficiently powerful sufficient to operate independently, resulting to combustion motors using gasoline for almost one-third of the distance completed in EV mode.

Policy and Economic Implications

According to calculations, the underestimation of PHEV CO2 output allowed four major automaker groups to avoid over €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ targets.

Additionally, owners of PHEVs could spend approximately €500 extra per year in operating costs than would be assumed under lab conditions.

“The strong claims that manufacturers often promote about their plug-in hybrid cars are obviously way off the truth,” commented a automotive expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are only slightly better than regular gas and diesel cars in terms of fuel use, CO₂ emissions, and operating costs.”

Policy Debate and Industry Lobbying

Hybrid cars have lately been drawn back into political discussions as carmakers have lobbied the EU to relax CO₂ standards. A planned ban on new combustion engine cars in 2035 has faced intense lobbying from the automotive sector and resistance from EU countries with large automotive industries.

Several senior officials have proposed plug-in hybrids as a potential “flexibility” solution to introduce in the legislation.

One external energy policy specialist, who was not involved with the research, described the report a “highly valuable addition” after a long period in which segments of the car industry argued there was insufficient data to accurately evaluate actual emissions.

“These findings show, without question, that the difference in official and actual PHEV energy use and CO₂ output is much, much larger than for gasoline or conventional cars,” they stated. “Any policy adjustments concerning PHEVs should be implemented with extreme caution and considering that evidence.”