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Plug-in hybrid electric vehicles produce almost five times greater global warming pollution than official figures show, according to a new report.

Widening Gap Between Lab and Real-World Emissions

Statistics reveals that PHEVs emit only 19% lower CO₂ than conventional petrol and diesel cars, based on analysis carried out by a advocacy organization. This contrasts sharply with laboratory tests, which suggested a three-quarters decrease in pollution.

Researchers studied data from onboard fuel consumption meters of 800,000 cars sold in the EU between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official estimates, up from three and a half times in 2021.

“Real-world CO2 output are increasing, while lab-reported figures are decreasing,” said a senior analyst involved in the report. “That discrepancy is growing and creates a significant issue. Consequently, PHEVs emit nearly as much as gasoline cars.”

Key Factors Behind the Emissions Gap

Researchers attributed most of the gap to inflated estimates of the “utility factor” – the percentage of kilometers travelled in battery mode compared to total mileage. The team determined that only 27% of travel was done in EV mode, whereas lab assumptions assumed 84%.

Additionally, when operating in EV mode, pollution levels were significantly higher than official estimates. This happened because electric motors were insufficiently powerful sufficient to operate alone, leading to combustion motors burning gasoline for nearly a third of the distance completed in electric mode.

Policy and Financial Implications

Based on estimates, the lowballing of PHEV emissions allowed four large carmaker companies to avoid more than €5bn in penalties from 2021 and 2023, by falsely easing adherence with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs could spend approximately €500 more annually in running expenses than would be estimated under lab conditions.

“The bold statements that automakers like to make about their plug-in hybrid vehicles are clearly far from the mark,” commented a automotive analyst. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating expenses.”

Policy Debate and Automotive Pressure

Plug-in hybrid cars have lately been brought again into political discussions as automakers have pressed the European Union to weaken CO₂ standards. A proposed prohibition on new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive industry and resistance from EU countries with significant automotive industries.

Some high-level officials have suggested plug-in hybrids as a potential “flexibility” solution to introduce in the regulation.

One independent energy economics expert, who was unaffiliated with the research, described the report a “very useful contribution” after years in which segments of the automotive industry claimed there was too little information to properly evaluate real-world CO2 output.

“These findings show, without question, that the difference between official and real-world PHEV fuel consumption and CO₂ emissions is significantly greater than for petrol or diesel cars,” they stated. “All policy changes concerning PHEVs should be made with extreme caution and in the light of that data.”