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Plug-in hybrid electric vehicles produce almost five times more planet-heating emissions than lab-reported data indicate, as per a recent report.

Widening Gap In Official and Actual Emissions

Data reveals that PHEVs emit just 19% lower CO₂ than conventional petrol and diesel vehicles, according to analysis conducted by a non-profit group. That differs significantly with lab tests, which suggested a three-quarters reduction in emissions.

Analysts studied information from onboard energy use meters of 800,000 vehicles registered in Europe between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, increased from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported figures are falling,” said a lead analyst participating in the report. “This discrepancy is widening and creates a serious issue. Consequently, PHEVs pollute almost as heavily as petrol vehicles.”

Primary Reasons Behind the Emissions Gap

Researchers attributed most of the gap to overestimates of the “electric driving share” – the percentage of miles travelled in electric mode relative to overall mileage. The team found that only 27% of driving was done in EV mode, whereas official estimates assumed 84%.

Additionally, when operating in electric mode, pollution amounts were significantly higher than lab estimates. This happened because electric motors were insufficiently powerful enough to function independently, resulting to engines burning gasoline for almost a third of the distance completed in EV mode.

Policy and Economic Implications

According to estimates, the underestimation of PHEV CO2 output enabled several major carmaker companies to avoid more than €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs would pay approximately €500 extra per year in running costs than would be estimated under laboratory tests.

“The strong statements that automakers like to make about their PHEV vehicles are obviously way off the mark,” commented a automotive expert. “Buyers are being misled into believing that by buying a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are little improved than standard petrol and diesel vehicles in terms of fuel consumption, CO₂ production, and running expenses.”

Policy Discussion and Industry Lobbying

Plug-in hybrid vehicles have recently been brought again into policy debates as carmakers have lobbied the European Union to weaken CO₂ targets. A planned prohibition on new internal combustion vehicles in 2035 has faced intense lobbying from the car sector and resistance from EU countries with large car industries.

Several high-level officials have proposed PHEVs as a potential “compromise” option to introduce in the regulation.

An independent energy policy specialist, who was not involved with the research, called the report a “highly valuable addition” after a long period in which segments of the car industry claimed there was too little information to properly assess real-world emissions.

“These findings show, beyond any doubt, that the difference in official and actual PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or conventional cars,” the expert said. “All regulatory adjustments regarding PHEVs should be implemented with utmost caution and in the light of that evidence.”