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PHEVs produce almost five times greater planet-heating emissions than lab-reported data indicate, according to a recent report.

Widening Gap Between Lab and Actual Emissions

Statistics shows that PHEVs release just one-fifth lower CO₂ than conventional petrol and diesel vehicles, based on research conducted by a advocacy group. That contrasts significantly with laboratory estimates, which suggested a three-quarters decrease in emissions.

Researchers studied data from onboard energy use meters of 800,000 vehicles sold in Europe from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than official estimates, increased from three and a half times in 2021.

“Actual emissions are rising, while lab-reported emissions are decreasing,” said a senior analyst participating in the report. “This discrepancy is widening and poses a serious issue. Consequently, PHEVs pollute almost as heavily as petrol cars.”

Primary Factors Behind the Discrepancy

Researchers attributed the majority of the gap to inflated estimates of the “utility factor” – the percentage of kilometers travelled in battery mode compared to total distance. They determined that only a quarter of driving was completed in electric mode, while official assumptions suggested 84%.

Even, when running in EV mode, pollution amounts were well above lab estimates. This happened because electric motors were insufficiently powerful enough to operate alone, leading to engines burning fossil fuels for nearly a third of the travel completed in electric mode.

Regulatory and Economic Implications

Based on calculations, the lowballing of PHEV emissions enabled several large automaker groups to escape over €5bn in penalties from 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs would pay approximately €500 extra annually in running costs than would be assumed under laboratory conditions.

“The strong claims that automakers like to make about their plug-in hybrid cars are obviously way off the mark,” commented a transport analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the environment and cutting money. In reality, PHEVs are little better than regular gas and diesel cars in terms of energy use, CO₂ production, and operating expenses.”

Political Debate and Automotive Pressure

Hybrid cars have recently been brought again into political debates as carmakers have pressed the European Union to weaken CO₂ targets. A planned ban on sales of new combustion engine cars in 2035 has faced heavy lobbying from the automotive sector and resistance from member states with large car manufacturing.

Some senior officials have suggested plug-in hybrids as a potential “flexibility” solution to introduce in the regulation.

An external energy economics expert, who was unaffiliated with the research, described the analysis a “highly valuable addition” after a long period in which parts of the automotive industry claimed there was too little data to accurately evaluate real-world emissions.

“These findings show, without question, that the difference in lab and actual PHEV energy use and CO₂ output is significantly greater than for gasoline or conventional cars,” the expert said. “Any policy adjustments regarding PHEVs should be made with extreme care and in the light of this evidence.”