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Plug-in hybrid electric vehicles release nearly 5x greater global warming emissions than lab-reported data indicate, according to a new analysis.

Growing Discrepancy Between Lab and Actual Emissions

Statistics reveals that PHEVs release just one-fifth lower CO₂ than conventional gas and diesel cars, based on analysis conducted by a advocacy group. This contrasts significantly with laboratory tests, which suggested a three-quarters decrease in pollution.

Analysts studied information from in-vehicle energy use meters of eight hundred thousand cars sold in the EU between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than official figures, up from three and a half times in 2021.

“Actual emissions are increasing, while official figures are decreasing,” said a senior analyst participating in the report. “That gap is widening and poses a serious issue. Consequently, PHEVs pollute nearly as much as gasoline vehicles.”

Key Factors Driving the Emissions Gap

Researchers attributed the majority of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in electric mode compared to overall mileage. The team found that only 27% of driving was completed in electric mode, whereas official estimates assumed 84%.

Even, when operating in electric mode, emission amounts were well above official estimates. This happened because electric motors were not strong sufficient to function alone, leading to engines using gasoline for nearly one-third of the distance covered in EV mode.

Policy and Financial Implications

Based on estimates, the lowballing of PHEV CO2 output allowed four major carmaker groups to avoid more than €5bn in fines from 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs could pay approximately €500 extra per year in operating expenses than would be assumed under laboratory conditions.

“The bold claims that manufacturers like to make about their PHEV cars are clearly far from the mark,” commented a automotive expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are helping the planet and cutting money. Actually, PHEVs are only slightly better than standard petrol and diesel cars in terms of energy use, CO₂ production, and operating expenses.”

Political Debate and Automotive Pressure

Plug-in hybrid cars have recently been brought back into political discussions as carmakers have lobbied the European Union to relax CO₂ targets. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the car sector and opposition from EU countries with large automotive industries.

Several high-level politicians have proposed plug-in hybrids as a potential “compromise” option to introduce in the legislation.

An external energy policy specialist, who was unaffiliated with the research, described the analysis a “highly valuable contribution” after years in which parts of the automotive industry claimed there was insufficient data to properly assess actual emissions.

“These findings demonstrate, without question, that the difference in official and actual PHEV fuel consumption and CO₂ output is much, much larger than for petrol or conventional cars,” the expert stated. “All policy adjustments regarding PHEVs should be made with extreme caution and in the light of this data.”