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PHEVs release almost 5x more global warming pollution than lab-reported figures show, according to a recent report.

Growing Discrepancy In Lab and Real-World CO2 Output

Statistics reveals that PHEVs release just one-fifth lower CO₂ than traditional petrol and diesel cars, according to analysis conducted by a non-profit group. This contrasts sharply with laboratory estimates, which suggested a 75% decrease in pollution.

Analysts examined information from in-vehicle energy use meters of 800,000 vehicles sold in the EU between 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than lab estimates, increased from three and a half times in 2021.

“Real-world emissions are rising, while official emissions are decreasing,” said a senior analyst involved in the report. “That gap is widening and poses a serious problem. Consequently, PHEVs emit almost as heavily as gasoline cars.”

Primary Factors Driving the Emissions Gap

Researchers linked the majority of the difference to inflated estimates of the “utility factor” – the percentage of miles travelled in electric mode compared to total mileage. They found that just 27% of driving was completed in electric mode, whereas official assumptions suggested 84%.

Even, when operating in EV mode, pollution levels were significantly higher than official estimates. That happened because electric motors were not strong enough to operate independently, resulting to engines burning gasoline for nearly a third of the travel completed in EV mode.

Policy and Economic Implications

According to estimates, the underestimation of PHEV emissions allowed four major automaker companies to escape more than €5bn in penalties from 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ standards.

Additionally, drivers of PHEVs could pay about €500 more per year in operating expenses than would be estimated under lab tests.

“The bold statements that automakers often promote about their plug-in hybrid vehicles are obviously far from the mark,” stated a transport analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and cutting money. Actually, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of fuel use, CO₂ production, and running costs.”

Policy Discussion and Industry Pressure

Plug-in hybrid cars have recently been brought back into policy discussions as carmakers have pressed the European Union to relax CO₂ targets. 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 high-level officials have proposed plug-in hybrids as a possible “flexibility” solution to introduce in the legislation.

An external energy economics expert, who was not involved with the research, described the report a “very useful contribution” after a long period in which segments of the automotive sector claimed there was insufficient data to properly evaluate real-world emissions.

“These findings show, beyond any doubt, that the gap in lab and real-world PHEV energy use and CO₂ emissions is much, much greater than for petrol or diesel vehicles,” the expert stated. “Any policy adjustments regarding PHEVs should be implemented with utmost caution and considering that data.”