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Plug-in hybrid cars release nearly 5x more planet-heating emissions than lab-reported figures show, as per a new analysis.

Growing Gap Between Official and Actual Emissions

Statistics reveals that PHEVs release just one-fifth less CO₂ than conventional gas and diesel vehicles, according to research conducted by a advocacy group. That contrasts significantly with laboratory estimates, which suggested a three-quarters decrease in emissions.

Researchers studied data from onboard energy use monitors of 800,000 vehicles sold in the EU between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, increased from 3.5 times in 2021.

“Real-world emissions are rising, while official figures are falling,” stated a senior analyst involved in the report. “That discrepancy is widening and poses a significant issue. Consequently, PHEVs emit nearly as much as gasoline vehicles.”

Primary Factors Driving the Emissions Gap

Researchers linked most of the gap to overestimates of the “electric driving share” – the percentage of miles travelled in battery power relative to total distance. The team found that only a quarter of travel was completed in electric mode, whereas lab assumptions suggested over four-fifths.

Even, when running in EV mode, pollution levels were significantly higher than official estimates. This happened because EV motors were not strong enough to operate independently, leading to engines burning gasoline for almost a third of the distance completed in EV mode.

Regulatory and Economic Implications

Based on calculations, the lowballing of PHEV emissions enabled four large automaker groups to avoid over €5bn in fines between 2021 and 2023, by artificially easing adherence with European Union average fleet CO₂ targets.

Additionally, owners of PHEVs would spend approximately €500 extra per year in operating costs than would be assumed under lab conditions.

“The bold statements that automakers like to make about their PHEV cars are clearly way off the mark,” commented a transport analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are little better than standard petrol and diesel vehicles in terms of energy consumption, CO₂ production, and running expenses.”

Policy Discussion and Automotive Pressure

Plug-in hybrid vehicles have lately been drawn again into policy debates as automakers have pressed the EU to relax CO₂ standards. A planned prohibition on sales of new internal combustion cars in 2035 has faced heavy lobbying from the car sector and resistance from member states with significant car manufacturing.

Some high-level officials have suggested plug-in hybrids as a potential “flexibility” option to include in the legislation.

One independent energy policy specialist, who was not involved with the study, described the report a “highly valuable contribution” after a long period in which parts of the car industry claimed there was too little information to properly evaluate real-world CO2 output.

“The results show, beyond any doubt, that the difference between lab and actual PHEV fuel consumption and CO₂ output is much, much greater than for petrol or diesel vehicles,” the expert stated. “All policy adjustments regarding PHEVs should be made with extreme caution and in the light of this data.”