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Plug-in hybrid cars emit nearly 5x more global warming pollution than official data indicate, as per a new analysis.

Widening Discrepancy Between Lab and Actual Emissions

Statistics shows that PHEVs emit just 19% lower CO₂ than conventional gas and diesel cars, according to research conducted by a non-profit group. This differs sharply with lab estimates, which suggested a 75% reduction in pollution.

Analysts examined data from in-vehicle fuel consumption meters of eight hundred thousand vehicles registered in Europe from 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab estimates, up from 3.5 times in 2021.

“Real-world emissions are rising, while official figures are decreasing,” stated a senior researcher participating in the report. “This discrepancy is widening and poses a significant problem. Consequently, PHEVs pollute nearly as heavily as petrol cars.”

Key Factors Driving the Emissions Gap

Analysts linked the majority of the difference to inflated estimates of the “utility factor” – the ratio of miles travelled in electric power compared to overall mileage. They determined that only a quarter of travel was completed in EV mode, while lab assumptions suggested over four-fifths.

Even, when running in EV mode, emission amounts were significantly higher than lab estimates. This happened because EV motors were not strong enough to operate alone, resulting to combustion motors burning gasoline for almost a third of the distance completed in electric mode.

Policy and Economic Consequences

Based on estimates, the underestimation of PHEV emissions allowed four major carmaker groups to escape more than €5bn in penalties between 2021 and 2023, by falsely easing adherence with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs could spend about €500 extra annually in running expenses than would be estimated under laboratory tests.

“The strong statements that manufacturers like to make about their PHEV vehicles are clearly way off the truth,” commented a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are little improved than standard gas and diesel vehicles in terms of energy use, CO₂ production, and running costs.”

Political Discussion and Automotive Lobbying

Plug-in hybrid vehicles have lately been drawn again into political debates as carmakers have lobbied the EU to relax CO₂ targets. A planned ban on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the car sector and opposition from EU countries with significant automotive manufacturing.

Several senior politicians have suggested plug-in hybrids as a possible “flexibility” solution to include in the regulation.

An external energy economics specialist, who was not involved with the study, described the analysis a “very useful contribution” after a long period in which segments of the automotive sector claimed there was too little data to properly assess actual CO2 output.

“The results demonstrate, beyond any doubt, that the difference between lab and actual PHEV energy use and CO₂ emissions is significantly larger than for petrol or conventional vehicles,” they said. “Any policy changes regarding PHEVs should be made with extreme caution and in the light of that evidence.”