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PHEVs produce nearly five times greater planet-heating pollution than lab-reported figures show, according to a new report.

Widening Gap In Official and Real-World Emissions

Data shows that PHEVs emit just 19% lower CO₂ than traditional gas and diesel cars, based on analysis conducted by a non-profit group. That differs significantly with laboratory tests, which assumed a three-quarters reduction in pollution.

Researchers studied information from in-vehicle energy use meters of 800,000 cars sold in the EU from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than official estimates, up from three and a half times in 2021.

“Actual CO2 output are rising, while official figures are falling,” stated a lead researcher involved in the report. “That discrepancy is growing and creates a significant problem. As a result, PHEVs pollute nearly as much as petrol vehicles.”

Primary Reasons Behind the Discrepancy

Researchers attributed most of the difference to overestimates of the “electric driving share” – the percentage of kilometers driven in battery power compared to overall distance. The team determined that only 27% of travel was done in electric mode, while lab assumptions assumed 84%.

Even, when operating in EV mode, pollution levels were significantly higher than lab projections. This happened because EV motors were not strong sufficient to function independently, resulting to engines using fossil fuels for almost one-third of the distance completed in EV mode.

Regulatory and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output allowed four large carmaker groups to escape over €5bn in penalties from 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ targets.

Furthermore, drivers of PHEVs would spend approximately €500 extra annually in running expenses than would be estimated under lab tests.

“The bold claims that manufacturers like to make about their plug-in hybrid vehicles are clearly way off the mark,” commented a automotive expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and saving costs. In reality, PHEVs are little improved than regular petrol and diesel cars in terms of fuel use, CO₂ emissions, and running costs.”

Policy Discussion and Automotive Lobbying

Hybrid cars have lately been drawn again into policy debates as automakers have lobbied the European Union to relax CO₂ standards. A planned ban on new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive industry and opposition from EU countries with large car manufacturing.

Several senior officials have suggested PHEVs as a possible “compromise” solution to include in the regulation.

One independent energy economics expert, who was not involved with the research, called the analysis a “very useful contribution” after years in which segments of the car sector claimed there was insufficient data to accurately evaluate real-world CO2 output.

“The results demonstrate, without question, that the difference in lab and actual PHEV energy use and CO₂ emissions is much, much larger than for gasoline or diesel cars,” they stated. “All regulatory adjustments regarding PHEVs should be made with utmost caution and in the light of this evidence.”