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Plug-in hybrid electric vehicles produce nearly five times more global warming pollution than lab-reported data show, according to a new analysis.

Widening Gap In Lab and Actual Emissions

Statistics shows that PHEVs emit only one-fifth less CO₂ than conventional gas and diesel cars, according to research conducted by a advocacy organization. That contrasts significantly with laboratory tests, which assumed a 75% reduction in emissions.

Researchers studied data from in-vehicle energy use meters of 800,000 cars registered in Europe from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are falling,” said a lead researcher involved in the report. “This gap is widening and creates a serious problem. As a result, PHEVs emit almost as heavily as gasoline vehicles.”

Primary Reasons Driving the Discrepancy

Analysts attributed most of the gap to overestimates of the “utility factor” – the ratio of kilometers travelled in electric power relative to total mileage. They found that just 27% of driving was completed in EV mode, while lab estimates suggested over four-fifths.

Additionally, when operating in EV mode, pollution amounts were well above official projections. That happened because electric motors were insufficiently powerful sufficient to operate alone, resulting to engines burning fossil fuels for almost a third of the travel covered in EV mode.

Policy and Financial Implications

According to calculations, the lowballing of PHEV CO2 output allowed several major automaker companies to avoid more than €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ targets.

Furthermore, drivers of PHEVs could spend approximately €500 extra per year in operating costs than would be estimated under laboratory conditions.

“The bold statements that manufacturers like to make about their plug-in hybrid cars are clearly way off the truth,” commented a transport expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and saving costs. In reality, PHEVs are little improved than standard gas and diesel cars in terms of fuel use, CO₂ emissions, and operating costs.”

Political Debate and Industry Pressure

Hybrid vehicles have lately been brought again into political debates as automakers have lobbied the European Union to relax CO₂ targets. A proposed prohibition on new internal combustion cars in 2035 has faced heavy lobbying from the automotive industry and resistance from member states with large automotive manufacturing.

Some high-level politicians have suggested PHEVs as a possible “compromise” option to include in the regulation.

An external energy economics expert, who was unaffiliated with the research, described the report a “highly valuable addition” after years in which segments of the car industry argued there was insufficient information to properly assess real-world CO2 output.

“The results demonstrate, without question, that the gap between official and real-world PHEV energy use and CO₂ output is much, much greater than for petrol or diesel cars,” the expert stated. “All policy adjustments regarding PHEVs should be made with extreme care and considering that data.”