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PHEVs emit almost 5x greater planet-heating emissions than lab-reported figures show, according to a new report.

Growing Gap In Official and Actual CO2 Output

Statistics shows that PHEVs release just 19% lower CO₂ than traditional gas and diesel vehicles, based on research carried out by a advocacy group. That differs significantly with laboratory tests, which assumed a 75% decrease in emissions.

Researchers examined information from in-vehicle energy use monitors of 800,000 vehicles sold in the EU between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, up from three and a half times in 2021.

“Actual emissions are rising, while lab-reported emissions are decreasing,” said a senior researcher participating in the report. “This gap is widening and poses a serious issue. Consequently, PHEVs emit almost as much as petrol vehicles.”

Primary Factors Behind the Discrepancy

Analysts linked the majority of the difference to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in battery power compared to total distance. The team found that only 27% of travel was completed in electric mode, whereas lab assumptions suggested 84%.

Even, when operating in electric mode, pollution amounts were well above lab projections. This happened because electric motors were not strong enough to operate alone, resulting to combustion motors using gasoline for almost a third of the distance completed in EV mode.

Regulatory and Financial Consequences

Based on estimates, the lowballing of PHEV CO2 output allowed four large automaker companies to avoid more than €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ targets.

Additionally, drivers of PHEVs could spend about €500 more annually in running costs than is estimated under lab conditions.

“The strong statements that manufacturers like to make about their plug-in hybrid cars are obviously way off the truth,” commented a automotive expert. “Buyers are being misled into thinking that by buying a PHEV, they are helping the environment and cutting money. Actually, PHEVs are little improved than regular petrol and diesel vehicles in terms of energy use, CO₂ emissions, and running costs.”

Political Discussion and Automotive Pressure

Plug-in hybrid cars have recently been drawn back into policy debates as carmakers have lobbied the EU to weaken CO₂ targets. A proposed prohibition on sales of new internal combustion cars in 2035 has faced heavy pressure from the automotive industry and opposition from member states with large automotive manufacturing.

Several high-level officials have proposed plug-in hybrids as a potential “flexibility” option to include in the legislation.

An independent energy policy expert, who was not involved with the research, called the report a “very useful contribution” after years in which segments of the car industry argued there was insufficient data to properly evaluate actual emissions.

“These findings demonstrate, beyond any doubt, that the difference between official and actual PHEV fuel consumption and CO₂ emissions is significantly greater than for gasoline or diesel vehicles,” they stated. “All regulatory adjustments concerning PHEVs should be made with utmost caution and in the light of that evidence.”