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Plug-in hybrid cars release nearly five times greater planet-heating emissions than lab-reported figures indicate, as per a new analysis.

Widening Discrepancy In Official and Actual CO2 Output

Statistics shows that PHEVs emit only 19% less CO₂ than conventional petrol and diesel vehicles, according to analysis conducted by a non-profit organization. This contrasts sharply with laboratory estimates, which assumed a 75% decrease in pollution.

Researchers examined information from onboard fuel consumption monitors of eight hundred thousand vehicles registered in the EU from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported figures are decreasing,” stated a lead analyst involved in the report. “This gap is growing and creates a significant issue. As a result, PHEVs pollute nearly as heavily as petrol vehicles.”

Primary Factors Driving the Discrepancy

Researchers attributed the majority of the difference to overestimates of the “electric driving share” – the ratio of miles travelled in battery power relative to overall distance. They determined that just a quarter of travel was completed in EV mode, while lab estimates suggested 84%.

Even, when running in electric mode, emission amounts were well above official estimates. This happened because EV motors were not strong sufficient to function independently, resulting to engines using fossil fuels for almost one-third of the travel completed in EV mode.

Policy and Financial Consequences

According to calculations, the lowballing of PHEV CO2 output allowed four large automaker companies to escape more than €5bn in fines between 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs would spend about €500 extra per year in running expenses than would be assumed under laboratory conditions.

“The bold claims that automakers often promote about their PHEV cars are clearly far from the truth,” stated a transport expert. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are little better than regular petrol and diesel cars in terms of fuel use, CO₂ emissions, and running expenses.”

Policy Debate and Industry Pressure

Plug-in hybrid cars have lately been drawn back into political debates as carmakers have pressed the EU to relax CO₂ standards. A planned ban on sales of new internal combustion cars in 2035 has faced heavy pressure from the automotive industry and opposition from EU countries with significant automotive industries.

Several high-level politicians have proposed plug-in hybrids as a possible “compromise” solution to introduce in the regulation.

One independent energy policy expert, who was not involved with the research, described the analysis a “highly valuable contribution” after years in which segments of the car sector argued there was too little data to properly evaluate actual CO2 output.

“These findings show, without question, that the gap between lab and real-world PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or conventional vehicles,” the expert stated. “All regulatory changes regarding PHEVs should be made with extreme care and considering this evidence.”