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PHEVs produce almost 5x greater planet-heating pollution than lab-reported figures show, according to a new analysis.

Growing Gap Between Official and Actual Emissions

Data reveals that PHEVs release only 19% lower CO₂ than traditional petrol and diesel cars, according to analysis carried out by a advocacy group. This differs sharply with lab estimates, which assumed a 75% reduction in emissions.

Researchers examined data from onboard fuel consumption meters of 800,000 vehicles registered in Europe between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, increased from three and a half times in 2021.

“Actual emissions are rising, while official figures are decreasing,” stated a senior researcher involved in the study. “That discrepancy is widening and creates a serious problem. Consequently, PHEVs pollute almost as heavily as gasoline vehicles.”

Key Factors Driving the Emissions Gap

Analysts attributed most of the gap to inflated estimates of the “electric driving share” – the ratio of miles travelled in battery mode relative to overall distance. The team determined that just a quarter of driving was completed in EV mode, while official assumptions assumed over four-fifths.

Additionally, when running in electric mode, emission amounts were well above lab estimates. That happened because EV motors were not strong enough to function alone, resulting to combustion motors burning gasoline for almost one-third of the travel covered in electric mode.

Regulatory and Financial Implications

Based on estimates, the lowballing of PHEV emissions enabled several major automaker groups to escape over €5bn in fines between 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs could spend about €500 more annually in running costs than is assumed under laboratory conditions.

“The strong statements that automakers often promote about their PHEV vehicles are obviously far from the mark,” stated a transport expert. “Consumers are being misled into thinking that by buying a PHEV, they are helping the planet and saving money. In reality, PHEVs are little improved than regular petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and running costs.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid cars have recently been brought back into political debates as automakers have pressed the EU to weaken CO₂ targets. A proposed ban on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the car industry and opposition from EU countries with significant car manufacturing.

Several high-level officials have proposed plug-in hybrids as a possible “flexibility” solution to include in the legislation.

One independent energy economics expert, who was not involved with the research, called the analysis a “very useful addition” after years in which segments of the automotive industry claimed there was too little information to accurately evaluate real-world emissions.

“The results show, beyond any doubt, that the difference in lab and real-world PHEV fuel consumption and CO₂ emissions is much, much greater than for gasoline or diesel vehicles,” the expert said. “All regulatory adjustments concerning PHEVs should be made with utmost caution and considering that evidence.”