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Plug-in hybrid cars release nearly five times more planet-heating pollution than lab-reported data indicate, according to a recent analysis.

Growing Gap Between Lab and Actual Emissions

Statistics reveals that PHEVs release only one-fifth less CO₂ than traditional petrol and diesel cars, according to research conducted by a non-profit organization. That differs significantly with laboratory estimates, which suggested a 75% decrease in pollution.

Researchers examined data from in-vehicle fuel consumption meters of 800,000 cars registered in Europe from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, up from 3.5 times in 2021.

“Actual emissions are increasing, while official figures are decreasing,” said a lead researcher participating in the report. “That discrepancy is widening and poses a serious problem. Consequently, PHEVs emit nearly as much as gasoline vehicles.”

Key Reasons Behind the Discrepancy

Analysts attributed the majority of the difference to inflated estimates of the “utility factor” – the ratio of miles travelled in battery mode compared to overall distance. They determined that only 27% of driving was done in electric mode, while lab estimates suggested 84%.

Additionally, when running in electric mode, pollution levels were significantly higher than lab estimates. That happened because electric motors were insufficiently powerful enough to function independently, resulting to engines burning fossil fuels for nearly one-third of the distance completed in EV mode.

Policy and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output enabled four large carmaker companies to avoid more than €5bn in fines between 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs could spend approximately €500 more per year in operating expenses than would be assumed under lab conditions.

“The strong statements that manufacturers like to make about their PHEV cars are obviously way off the truth,” stated a automotive expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are little better than regular gas and diesel vehicles in terms of fuel use, CO₂ production, and operating expenses.”

Political Discussion and Industry Lobbying

Plug-in hybrid cars have lately been drawn back into political debates as carmakers have lobbied the European Union to relax CO₂ standards. A proposed ban on sales of new internal combustion cars in 2035 has faced heavy lobbying from the car sector and opposition from EU countries with significant automotive manufacturing.

Several high-level politicians have suggested PHEVs as a possible “flexibility” solution to include in the regulation.

One external energy policy expert, who was not involved with the research, described the analysis a “highly valuable addition” after years in which parts of the car sector claimed there was too little information to properly evaluate actual emissions.

“The results demonstrate, without question, that the difference in official and actual PHEV energy use and CO₂ output is significantly larger than for gasoline or conventional cars,” the expert stated. “All policy adjustments regarding PHEVs should be implemented with utmost care and considering that data.”