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Plug-in hybrid cars release almost 5x greater global warming pollution than lab-reported figures show, as per a new analysis.

Widening Gap In Lab and Actual CO2 Output

Data reveals that PHEVs release only 19% less CO₂ than conventional petrol and diesel cars, based on analysis conducted by a non-profit organization. That differs sharply with laboratory tests, which assumed a 75% decrease in pollution.

Researchers examined data from in-vehicle fuel consumption meters of 800,000 vehicles sold in the EU between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times greater than lab figures, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while official figures are decreasing,” said a senior researcher involved in the report. “This discrepancy is widening and poses a serious problem. Consequently, PHEVs emit nearly as much as petrol cars.”

Key Factors Driving the Discrepancy

Researchers linked most of the gap to overestimates of the “utility factor” – the ratio of kilometers driven in battery mode compared to total distance. The team found that only a quarter of travel was done in electric mode, whereas official assumptions suggested over four-fifths.

Additionally, when operating in electric mode, pollution levels were well above lab estimates. That occurred because electric motors were insufficiently powerful enough to operate independently, resulting to combustion motors burning fossil fuels for almost a third of the distance completed in EV mode.

Policy and Financial Consequences

Based on estimates, the lowballing of PHEV emissions allowed four large carmaker companies to avoid more than €5bn in fines between 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ standards.

Furthermore, owners of PHEVs would spend approximately €500 more annually in operating costs than is estimated under lab tests.

“The bold claims that manufacturers like to make about their plug-in hybrid cars are clearly far from the mark,” stated a automotive analyst. “Consumers are being misled into thinking that by purchasing a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of energy use, CO₂ production, and operating costs.”

Policy Debate and Automotive Pressure

Hybrid vehicles have recently been drawn back into policy discussions as automakers have lobbied the European Union to weaken CO₂ standards. A planned ban on sales of new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive sector and opposition from EU countries with large automotive manufacturing.

Some senior officials have proposed plug-in hybrids as a possible “flexibility” option to introduce in the regulation.

An external energy economics specialist, who was not involved with the research, described the report a “highly valuable addition” after years in which segments of the automotive sector argued there was insufficient data to properly assess real-world emissions.

“These findings show, beyond any doubt, that the difference between lab and actual PHEV energy use and CO₂ emissions is significantly larger than for petrol or conventional cars,” the expert stated. “Any policy adjustments concerning PHEVs should be implemented with utmost care and in the light of this data.”