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PHEVs produce almost 5x more planet-heating pollution than lab-reported figures show, according to a new report.

Growing Gap In Lab and Actual CO2 Output

Data shows that PHEVs emit only 19% less CO₂ than conventional petrol and diesel cars, based on analysis conducted by a advocacy organization. This differs sharply with lab tests, which assumed a three-quarters decrease in emissions.

Researchers examined data from in-vehicle energy use meters of eight hundred thousand cars sold in the EU from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, increased from three and a half times in 2021.

“Real-world emissions are rising, while official figures are decreasing,” said a lead analyst involved in the report. “That discrepancy is growing and creates a serious issue. As a result, PHEVs pollute almost as heavily as petrol vehicles.”

Primary Reasons Driving the Discrepancy

Researchers linked the majority of the gap to inflated estimates of the “electric driving share” – the ratio of miles travelled in battery mode compared to overall distance. The team found that just 27% of driving was completed in electric mode, whereas official estimates suggested 84%.

Additionally, when running in EV mode, emission amounts were significantly higher than lab estimates. This occurred because EV motors were not strong sufficient to operate independently, resulting to engines burning gasoline for nearly one-third of the distance completed in electric mode.

Policy and Financial Consequences

Based on estimates, the underestimation of PHEV CO2 output enabled four large automaker groups to escape over €5bn in fines from 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ standards.

Furthermore, drivers of PHEVs would pay approximately €500 extra per year in running costs than would be assumed under laboratory tests.

“The bold statements that automakers often promote about their plug-in hybrid vehicles are clearly far from the mark,” stated a automotive analyst. “Buyers are being misled into believing that by buying a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are little better than regular petrol and diesel cars in terms of energy consumption, CO₂ emissions, and running costs.”

Policy Discussion and Automotive Lobbying

Hybrid vehicles have lately been drawn again into policy debates as carmakers have pressed the EU to weaken CO₂ targets. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced intense lobbying from the car industry and resistance from member states with large automotive manufacturing.

Some high-level politicians have proposed PHEVs as a possible “compromise” solution to include in the legislation.

One external energy policy specialist, who was unaffiliated with the study, described the analysis a “very useful addition” after years in which segments of the car sector claimed there was too little data to accurately assess real-world emissions.

“These findings demonstrate, without question, that the difference in lab and actual PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or conventional cars,” the expert said. “All regulatory changes regarding PHEVs should be made with utmost care and considering that evidence.”