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PHEVs produce almost five times more planet-heating emissions than official figures show, according to a new report.

Widening Gap Between Official and Actual Emissions

Statistics shows that PHEVs release just 19% lower CO₂ than conventional petrol and diesel cars, based on research conducted by a advocacy organization. That contrasts significantly with laboratory tests, which assumed a 75% reduction in emissions.

Researchers studied data from onboard energy use monitors of eight hundred thousand cars registered in Europe from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while official figures are decreasing,” said a lead researcher involved in the report. “That gap is growing and creates a significant issue. As a result, PHEVs emit almost as heavily as gasoline cars.”

Key Factors Behind the Emissions Gap

Analysts linked most of the gap to overestimates of the “electric driving share” – the ratio of kilometers travelled in battery power relative to total mileage. They found that just 27% of driving was completed in EV mode, whereas official assumptions suggested 84%.

Additionally, when operating in electric mode, pollution amounts were well above lab projections. That happened because EV motors were insufficiently powerful sufficient to function independently, leading to combustion motors burning gasoline for almost a third of the distance completed in EV mode.

Policy and Financial Implications

Based on calculations, the lowballing of PHEV CO2 output allowed several major automaker groups to escape over €5bn in penalties from 2021 and 2023, by falsely easing compliance with European Union fleet-average CO₂ standards.

Furthermore, owners of PHEVs would pay approximately €500 extra annually in running expenses than would be assumed under lab tests.

“The strong statements that automakers like to make about their PHEV cars are obviously way off the mark,” stated a automotive expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are little improved than regular petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and running costs.”

Political Discussion and Automotive Lobbying

Plug-in hybrid vehicles have recently been drawn again into political debates as automakers have pressed the EU to weaken CO₂ standards. A planned prohibition on sales of new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive sector and opposition from member states with significant automotive industries.

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

One external energy policy expert, who was not involved with the research, described the report a “highly valuable addition” after years in which segments of the automotive industry argued there was too little data to properly evaluate actual CO2 output.

“These findings show, beyond any doubt, that the gap between lab and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or diesel vehicles,” they stated. “Any regulatory adjustments concerning PHEVs should be implemented with utmost caution and considering this data.”