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PHEVs release almost five times greater global warming pollution than lab-reported data show, according to a new report.

Widening Discrepancy In Official and Actual Emissions

Data reveals that PHEVs release only 19% lower CO₂ than traditional gas and diesel vehicles, according to analysis conducted by a non-profit organization. That differs sharply with laboratory estimates, which suggested a three-quarters reduction in emissions.

Researchers studied data from in-vehicle energy use meters of 800,000 cars sold in Europe from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than lab estimates, up from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported figures are decreasing,” said a lead analyst participating in the report. “That discrepancy is widening and poses a significant issue. Consequently, PHEVs pollute nearly as much as petrol cars.”

Key Reasons Behind the Emissions Gap

Analysts attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of miles driven in electric mode relative to overall mileage. They found that just 27% of driving was done in electric mode, while official assumptions suggested over four-fifths.

Even, when running in EV mode, emission levels were well above official estimates. This happened because EV motors were not strong enough to operate alone, leading to combustion motors burning fossil fuels for almost a third of the distance completed in electric mode.

Policy and Financial Implications

Based on estimates, the underestimation of PHEV emissions allowed four large automaker companies to avoid over €5bn in fines between 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ targets.

Additionally, owners of PHEVs would spend approximately €500 extra annually in operating costs than is estimated under lab conditions.

“The bold claims that manufacturers often promote about their plug-in hybrid cars are obviously far from the truth,” stated a automotive analyst. “Consumers are being misled into thinking that by purchasing a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are only slightly improved than regular petrol and diesel vehicles in terms of fuel use, CO₂ production, and operating expenses.”

Political Debate and Automotive Pressure

Hybrid cars have lately been brought again into policy debates as carmakers have lobbied the European Union to relax CO₂ targets. A planned ban on sales of new internal combustion cars in 2035 has faced intense lobbying from the automotive industry and resistance from member states with significant automotive manufacturing.

Several high-level officials have suggested plug-in hybrids as a possible “compromise” solution to introduce 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 segments of the automotive industry argued there was insufficient information to accurately evaluate real-world CO2 output.

“These findings show, without question, that the difference between official and real-world PHEV fuel consumption and CO₂ output is much, much larger than for petrol or conventional vehicles,” the expert stated. “All policy adjustments concerning PHEVs should be made with extreme care and in the light of that evidence.”