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Plug-in hybrid electric vehicles emit almost 5x greater planet-heating emissions than official figures show, as per a new report.

Growing Discrepancy Between Official and Actual Emissions

Data shows that PHEVs emit just one-fifth lower CO₂ than conventional gas and diesel vehicles, based on research conducted by a non-profit group. That contrasts significantly with laboratory tests, which assumed a three-quarters reduction in pollution.

Analysts studied data from onboard fuel consumption meters of eight hundred thousand vehicles registered in the EU between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official figures, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are decreasing,” said a lead researcher involved in the report. “This discrepancy is widening and creates a significant problem. Consequently, PHEVs emit nearly as much as gasoline cars.”

Key Factors Driving the Emissions Gap

Researchers attributed the majority of the gap to overestimates of the “electric driving share” – the ratio of miles travelled in battery mode relative to overall mileage. They found that just a quarter of driving was completed in EV mode, whereas lab assumptions suggested over four-fifths.

Additionally, when running in electric mode, emission levels were well above official estimates. That occurred because electric motors were not strong sufficient to function alone, leading to engines using gasoline for almost a third of the distance covered in EV mode.

Regulatory and Economic Implications

Based on calculations, the underestimation of PHEV emissions allowed four major carmaker companies to escape more than €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ standards.

Furthermore, drivers of PHEVs would spend approximately €500 extra per year in running expenses than is assumed under laboratory conditions.

“The strong statements that manufacturers like to make about their plug-in hybrid cars are obviously way off the truth,” commented a transport expert. “Consumers are being duped into thinking that by buying a PHEV, they are helping the environment and saving costs. In reality, PHEVs are only slightly improved than regular petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Policy Discussion and Industry Pressure

Plug-in hybrid cars have lately been brought back into political debates as automakers have lobbied the EU to weaken CO₂ standards. A planned prohibition on sales of new internal combustion cars in 2035 has faced heavy pressure from the car sector and resistance from member states with large car industries.

Several high-level politicians have suggested PHEVs as a possible “compromise” option to include in the regulation.

An independent energy policy specialist, who was unaffiliated with the research, described the report a “very useful contribution” after years in which segments of the car sector claimed there was too little data to accurately evaluate real-world CO2 output.

“The results demonstrate, without question, that the gap in official and actual PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or conventional cars,” they stated. “All regulatory adjustments regarding PHEVs should be implemented with extreme care and considering this evidence.”