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Plug-in hybrid cars release almost five times more planet-heating pollution than official data indicate, according to a new report.

Widening Discrepancy In Official and Actual CO2 Output

Statistics reveals that PHEVs release only 19% less CO₂ than conventional gas and diesel vehicles, according to analysis conducted by a advocacy group. That contrasts sharply with laboratory estimates, which suggested a 75% decrease in emissions.

Analysts examined information from in-vehicle fuel consumption monitors of eight hundred thousand vehicles registered in Europe between 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, increased from 3.5 times in 2021.

“Actual emissions are rising, while official emissions are decreasing,” stated a lead analyst participating in the report. “That discrepancy is widening and poses a serious problem. As a result, PHEVs pollute nearly as heavily as petrol vehicles.”

Key Factors Behind the Emissions Gap

Analysts linked most of the difference to inflated estimates of the “utility factor” – the percentage of miles travelled in electric power compared to overall mileage. They found that only a quarter of driving was completed in EV mode, whereas official assumptions suggested 84%.

Even, when running in EV mode, pollution amounts were well above lab projections. This occurred because EV motors were not strong enough to function alone, resulting to combustion motors using gasoline for nearly one-third of the distance completed in electric mode.

Policy and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output enabled several major automaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs would pay approximately €500 more per year in operating costs than would be estimated under lab tests.

“The strong statements that manufacturers like to make about their plug-in hybrid cars are clearly way off the truth,” commented a automotive 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 better than regular gas and diesel cars in terms of fuel consumption, CO₂ emissions, and operating costs.”

Political Debate and Automotive Lobbying

Plug-in hybrid cars have lately been brought again into policy debates as carmakers have pressed the EU to weaken CO₂ targets. A proposed ban on sales of new combustion engine vehicles in 2035 has faced intense pressure from the car sector and resistance from EU countries with large car industries.

Some senior officials have proposed plug-in hybrids as a potential “compromise” solution to introduce in the regulation.

An independent energy policy expert, who was not involved with the research, called the analysis a “very useful contribution” after years in which segments of the car industry claimed there was insufficient data to accurately assess actual emissions.

“These findings show, without question, that the gap in lab and actual PHEV fuel consumption and CO₂ output is much, much larger than for petrol or diesel cars,” the expert said. “All regulatory changes regarding PHEVs should be made with extreme caution and in the light of this data.”