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PHEVs emit almost five times more global warming emissions than lab-reported data show, according to a new analysis.

Widening Gap Between Lab and Real-World CO2 Output

Statistics shows that PHEVs release only 19% lower CO₂ than traditional petrol and diesel cars, based on analysis conducted by a advocacy group. That differs sharply with lab estimates, which suggested a 75% reduction in pollution.

Researchers examined data from onboard fuel consumption meters of 800,000 cars sold in the EU between 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, increased from three and a half times in 2021.

“Actual emissions are rising, while lab-reported emissions are decreasing,” said a lead researcher involved in the study. “That gap is growing and poses a serious issue. As a result, PHEVs pollute almost as much as gasoline vehicles.”

Primary Factors Driving the Emissions Gap

Researchers attributed most of the gap to overestimates of the “utility factor” – the percentage of miles driven in electric power compared to total distance. The team found that just a quarter of driving was completed in EV mode, whereas lab estimates suggested 84%.

Even, when operating in EV mode, pollution amounts were well above lab estimates. This happened because EV motors were insufficiently powerful sufficient to operate independently, resulting to combustion motors burning fossil fuels for almost one-third of the distance completed in electric mode.

Regulatory and Economic Implications

According to calculations, the lowballing of PHEV emissions allowed several large carmaker groups to escape more than €5bn in fines between 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ standards.

Additionally, drivers of PHEVs could pay about €500 more annually in running expenses than is estimated under laboratory conditions.

“The bold statements that automakers often promote about their plug-in hybrid vehicles are obviously far from the truth,” commented a transport analyst. “Consumers are being misled into thinking that by buying a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are little better than regular petrol and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running costs.”

Policy Debate and Automotive Lobbying

Plug-in hybrid vehicles have recently been brought back into policy discussions as automakers have lobbied the European Union to relax CO₂ targets. A planned prohibition on new combustion engine cars in 2035 has faced heavy lobbying from the automotive sector and opposition from member states with significant automotive industries.

Several senior officials have suggested plug-in hybrids as a possible “compromise” solution to include in the regulation.

One external energy economics expert, who was unaffiliated with the research, described the analysis a “very useful contribution” after a long period in which parts of the automotive sector claimed there was insufficient data to properly assess actual emissions.

“The results demonstrate, beyond any doubt, that the difference between lab and actual PHEV fuel consumption and CO₂ output is significantly larger than for petrol or diesel vehicles,” they stated. “Any policy adjustments concerning PHEVs should be implemented with extreme care and considering that evidence.”