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Plug-in hybrid cars produce nearly 5x more global warming emissions than lab-reported figures show, as per a new analysis.

Growing Discrepancy In Lab and Real-World Emissions

Statistics reveals that PHEVs emit only 19% lower CO₂ than conventional petrol and diesel cars, based on analysis conducted by a non-profit group. That contrasts significantly with laboratory estimates, which suggested a three-quarters reduction in pollution.

Researchers studied information from in-vehicle energy use monitors of 800,000 cars sold in Europe from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than official estimates, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are decreasing,” said a lead analyst participating in the study. “That discrepancy is widening and poses a serious problem. As a result, PHEVs emit almost as heavily as gasoline vehicles.”

Key Reasons Driving the Discrepancy

Researchers attributed most of the difference to inflated estimates of the “electric driving share” – the percentage of miles travelled in electric power compared to overall distance. They determined that just a quarter of driving was done in EV mode, while official estimates suggested over four-fifths.

Additionally, when running in electric mode, emission levels were significantly higher than lab projections. This happened because EV motors were insufficiently powerful enough to function alone, resulting to combustion motors burning gasoline for nearly one-third of the distance covered in EV mode.

Policy and Economic Implications

According to estimates, the lowballing of PHEV emissions allowed four major automaker groups to escape more than €5bn in fines between 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs could spend approximately €500 extra per year in running expenses than is estimated under lab conditions.

“The strong statements that manufacturers often promote about their plug-in hybrid vehicles are obviously way off the truth,” commented a automotive expert. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are little improved than standard petrol and diesel cars in terms of fuel use, CO₂ emissions, and operating costs.”

Political Debate and Industry Pressure

Plug-in hybrid cars have recently been drawn again into political debates as carmakers have lobbied the EU to relax CO₂ targets. A proposed prohibition on new combustion engine vehicles in 2035 has faced intense pressure from the automotive sector and resistance from EU countries with significant automotive industries.

Several senior politicians have proposed PHEVs as a possible “compromise” option to include in the regulation.

One external energy economics expert, who was not involved with the research, called the analysis a “very useful addition” after years in which parts of the car industry claimed there was insufficient data to properly assess actual CO2 output.

“The results show, beyond any doubt, that the gap in official and actual PHEV fuel consumption and CO₂ output is much, much greater than for petrol or conventional cars,” the expert stated. “All regulatory changes concerning PHEVs should be implemented with utmost care and considering that data.”