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Plug-in hybrid cars release almost five times more global warming emissions than official figures show, according to a new analysis.

Widening Gap Between Lab and Actual Emissions

Statistics reveals that PHEVs emit only 19% lower CO₂ than conventional petrol and diesel cars, based on analysis carried out by a advocacy group. That differs sharply with laboratory estimates, which assumed a three-quarters reduction in pollution.

Researchers studied data from in-vehicle fuel consumption meters of 800,000 vehicles sold in the EU from 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, increased from 3.5 times in 2021.

“Actual emissions are increasing, while official figures are falling,” said a senior analyst involved in the study. “This gap is widening and creates a serious issue. Consequently, PHEVs pollute almost as much as petrol vehicles.”

Primary Reasons Driving the Emissions Gap

Researchers attributed the majority of the difference to inflated estimates of the “utility factor” – the ratio of kilometers travelled in battery power relative to total distance. The team found that only a quarter of driving was completed in electric mode, whereas lab estimates suggested over four-fifths.

Even, when running in electric mode, emission levels were well above official estimates. This occurred because EV motors were insufficiently powerful enough to function independently, resulting to engines burning fossil fuels for almost one-third of the travel completed in EV mode.

Regulatory and Financial Consequences

According to estimates, the lowballing of PHEV emissions allowed four major carmaker groups to avoid over €5bn in fines between 2021 and 2023, by artificially easing compliance with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs could spend about €500 extra per year in running costs than is assumed under laboratory conditions.

“The bold statements that automakers often promote about their PHEV vehicles are clearly far from the truth,” commented a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are little better than regular petrol and diesel cars in terms of energy use, CO₂ production, and operating costs.”

Policy Debate and Automotive Pressure

Plug-in hybrid vehicles have lately been brought back into political debates as carmakers have pressed the European Union to weaken CO₂ standards. A planned ban on new internal combustion cars in 2035 has faced intense lobbying from the automotive sector and opposition from EU countries with large car manufacturing.

Several high-level officials have proposed PHEVs as a possible “flexibility” option to introduce in the regulation.

One external energy economics specialist, who was not involved with the research, called the report a “highly valuable contribution” after a long period in which parts of the car industry claimed there was insufficient data to properly assess real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the gap in lab and actual PHEV energy use and CO₂ output is much, much larger than for petrol or diesel vehicles,” the expert stated. “Any regulatory changes regarding PHEVs should be made with utmost caution and in the light of this evidence.”