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Plug-in hybrid cars produce nearly five times greater global warming pollution than official figures show, as per a new report.

Growing Discrepancy In Lab and Actual Emissions

Statistics shows that PHEVs release only one-fifth lower CO₂ than traditional gas and diesel vehicles, based on analysis carried out by a advocacy group. That contrasts sharply with lab estimates, which suggested a three-quarters decrease in pollution.

Researchers studied information from in-vehicle energy use meters of 800,000 cars sold in Europe from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, up from 3.5 times in 2021.

“Actual emissions are increasing, while official figures are decreasing,” said a senior researcher involved in the report. “That gap is widening and poses a serious issue. Consequently, PHEVs pollute nearly as much as gasoline vehicles.”

Key Reasons Driving the Emissions Gap

Analysts attributed the majority of the gap to overestimates of the “utility factor” – the percentage of miles travelled in battery mode relative to overall mileage. The team determined that just 27% of driving was completed in electric mode, while lab assumptions assumed over four-fifths.

Even, when running in electric mode, emission levels were well above official estimates. This occurred because electric motors were not strong sufficient to operate alone, leading to combustion motors burning fossil fuels for nearly a third of the distance covered in electric mode.

Regulatory and Economic Consequences

Based on estimates, the lowballing of PHEV CO2 output enabled several large carmaker companies to escape over €5bn in penalties from 2021 and 2023, by artificially easing compliance with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs could pay about €500 extra annually in running 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 mark,” stated a transport analyst. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are little better than standard gas and diesel cars in terms of energy consumption, CO₂ emissions, and operating costs.”

Policy Discussion and Automotive Pressure

Plug-in hybrid cars have recently been drawn again into policy discussions as carmakers have pressed the European Union to relax CO₂ standards. A planned ban on new combustion engine cars in 2035 has faced heavy pressure from the car sector and resistance from member states with large car industries.

Some senior politicians have suggested plug-in hybrids as a potential “flexibility” solution to include in the legislation.

An independent energy economics specialist, who was not involved with the research, called the report a “very useful addition” after years in which segments of the automotive sector argued there was too little data to accurately evaluate actual emissions.

“These findings show, beyond any doubt, that the difference between lab and actual PHEV fuel consumption and CO₂ output is much, much larger than for petrol or conventional cars,” they stated. “All policy changes regarding PHEVs should be made with extreme care and considering this data.”