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

Widening Discrepancy In Lab and Real-World CO2 Output

Data reveals that PHEVs emit only 19% less CO₂ than conventional gas and diesel vehicles, based on research conducted by a non-profit group. That differs sharply with laboratory tests, which assumed a 75% reduction in emissions.

Researchers studied information from in-vehicle fuel consumption meters of eight hundred thousand vehicles sold in the EU from 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were nearly five times greater than official estimates, increased from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported figures are falling,” stated a lead analyst participating in the report. “This discrepancy is growing and creates a serious issue. As a result, PHEVs emit almost as heavily as gasoline vehicles.”

Key Factors Driving the Emissions Gap

Researchers attributed most of the difference to inflated estimates of the “utility factor” – the percentage of miles travelled in electric mode compared to total mileage. The team found that only 27% of driving was completed in electric mode, while official estimates suggested over four-fifths.

Even, when running in EV mode, emission levels were well above official estimates. That happened because EV motors were not strong sufficient to function independently, leading to engines burning gasoline for nearly one-third of the distance covered in EV mode.

Policy and Economic Consequences

Based on calculations, the underestimation of PHEV CO2 output enabled several large carmaker companies to avoid more than €5bn in penalties between 2021 and 2023, by artificially easing adherence with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs would spend about €500 more annually in running costs than would be estimated under laboratory tests.

“The bold claims that automakers like to make about their PHEV vehicles are obviously far from the mark,” stated a automotive analyst. “Consumers are being duped into thinking that by buying a PHEV, they are helping the planet and saving money. In reality, PHEVs are little improved than regular petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and running expenses.”

Political Discussion and Industry Lobbying

Plug-in hybrid vehicles have recently been drawn again into political 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 lobbying from the automotive sector and resistance from EU countries with significant car manufacturing.

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

An independent energy policy expert, who was unaffiliated with the study, called the analysis a “very useful addition” after years in which parts of the automotive sector argued there was too little data to accurately assess actual emissions.

“These findings show, beyond any doubt, that the difference in lab and real-world PHEV fuel consumption and CO₂ output is much, much larger than for petrol or diesel cars,” they stated. “Any regulatory adjustments regarding PHEVs should be made with extreme care and considering this evidence.”