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Plug-in hybrid electric vehicles release almost 5x more planet-heating emissions than lab-reported data indicate, according to a new analysis.

Growing Discrepancy Between Lab and Actual CO2 Output

Data shows that PHEVs emit only 19% lower CO₂ than traditional gas and diesel vehicles, according to research carried out by a advocacy group. That contrasts sharply with lab tests, which suggested a 75% reduction in pollution.

Researchers studied information from onboard fuel consumption meters of eight hundred thousand cars sold in the EU between 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are decreasing,” said a lead researcher involved in the report. “That gap is widening and poses a significant problem. As a result, PHEVs pollute almost as much as gasoline cars.”

Key Reasons Driving the Emissions Gap

Analysts attributed the majority of the difference to inflated estimates of the “electric driving share” – the ratio of miles driven in battery mode compared to overall mileage. They found that just a quarter of travel was done in electric mode, whereas official estimates assumed 84%.

Additionally, when operating in EV mode, emission amounts were well above official estimates. This happened because EV motors were not strong sufficient to function alone, leading to engines using gasoline for nearly one-third of the distance completed in EV mode.

Policy and Financial Implications

According to calculations, the underestimation of PHEV CO2 output allowed several large carmaker companies to escape over €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs could spend approximately €500 extra per year in operating expenses than would be estimated under laboratory tests.

“The bold claims that manufacturers like to make about their PHEV vehicles are obviously way off the truth,” commented a automotive expert. “Buyers are being duped into believing that by buying a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are only slightly better than regular gas and diesel cars in terms of energy consumption, CO₂ emissions, and running costs.”

Policy Discussion and Industry Lobbying

Hybrid vehicles have lately been drawn back into policy debates as carmakers have lobbied the European Union to relax CO₂ standards. A planned prohibition on sales of new combustion engine cars in 2035 has faced heavy lobbying from the automotive sector and opposition from member states with large car industries.

Several senior politicians have proposed plug-in hybrids as a possible “flexibility” solution to include in the regulation.

An independent energy economics specialist, who was unaffiliated with the study, called the analysis a “very useful addition” after years in which segments of the automotive sector argued there was too little data to properly evaluate actual emissions.

“The results demonstrate, beyond any doubt, that the gap in lab and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or conventional cars,” they said. “All policy changes concerning PHEVs should be implemented with extreme caution and in the light of that evidence.”