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PHEVs produce nearly five times more planet-heating pollution than lab-reported data indicate, according to a new report.

Widening Gap Between Official and Actual Emissions

Statistics shows that PHEVs release just one-fifth less CO₂ than traditional gas and diesel vehicles, based on analysis conducted by a non-profit group. This differs sharply with lab estimates, which assumed a 75% reduction in emissions.

Analysts examined data from in-vehicle fuel consumption meters of 800,000 cars sold in Europe between 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab estimates, up from 3.5 times in 2021.

“Actual emissions are increasing, while lab-reported emissions are falling,” said a senior analyst involved in the study. “This discrepancy is growing and poses a significant issue. Consequently, PHEVs emit almost as heavily as petrol vehicles.”

Key Reasons Driving the Emissions Gap

Analysts attributed most of the difference to overestimates of the “electric driving share” – the percentage of miles travelled in electric mode relative to overall distance. They found that just a quarter of driving was completed in EV mode, whereas lab estimates assumed 84%.

Even, when running in EV mode, pollution amounts were significantly higher than official estimates. This occurred because EV motors were insufficiently powerful enough to operate alone, leading to engines using fossil fuels for nearly one-third of the distance covered in electric mode.

Policy and Economic Consequences

According to estimates, the lowballing of PHEV CO2 output allowed four major carmaker companies to escape over €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs would spend approximately €500 more annually in operating expenses than is estimated under lab tests.

“The strong statements that manufacturers like to make about their PHEV vehicles are obviously way off the truth,” stated a transport expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the environment and cutting costs. In reality, PHEVs are little improved than standard petrol and diesel cars in terms of energy consumption, CO₂ production, and operating costs.”

Policy Discussion and Automotive Pressure

Plug-in hybrid vehicles have recently been brought again into policy debates as carmakers have lobbied the EU to relax CO₂ targets. A proposed ban on sales of new internal combustion vehicles in 2035 has faced intense pressure from the car sector and resistance from EU countries with large car manufacturing.

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

An external energy economics specialist, who was unaffiliated with the study, called the analysis a “very useful addition” after a long period in which segments of the car sector claimed there was insufficient information to properly assess actual CO2 output.

“The results show, beyond any doubt, that the gap in lab and actual PHEV energy use and CO₂ output is significantly greater than for petrol or conventional cars,” they stated. “All regulatory changes concerning PHEVs should be implemented with extreme care and considering this evidence.”