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Plug-in hybrid cars emit nearly five times more global warming emissions than lab-reported figures show, according to a recent report.

Widening Gap Between Official and Actual CO2 Output

Data shows that PHEVs release only 19% lower CO₂ than traditional gas and diesel cars, based on research conducted by a advocacy organization. That contrasts significantly with lab tests, which assumed a 75% reduction in emissions.

Analysts studied information from in-vehicle fuel consumption meters of 800,000 vehicles sold in the EU between 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, up from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported figures are falling,” said a senior analyst involved in the report. “This discrepancy is widening and poses a serious problem. As a result, PHEVs pollute nearly as heavily as petrol cars.”

Primary Reasons Behind the Emissions Gap

Analysts linked the majority of the gap to overestimates of the “utility factor” – the percentage of miles driven in electric mode compared to total distance. They determined that only a quarter of travel was done in EV mode, while lab assumptions suggested 84%.

Even, when running in EV mode, emission amounts were significantly higher than lab projections. This happened because EV motors were insufficiently powerful enough to operate independently, resulting to combustion motors burning fossil fuels for almost a third of the travel completed in EV mode.

Regulatory and Economic Implications

Based on estimates, the lowballing of PHEV CO2 output enabled four major automaker groups to avoid over €5bn in fines from 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ standards.

Furthermore, drivers of PHEVs could spend approximately €500 extra annually in running costs than would be estimated under lab conditions.

“The strong statements that automakers often promote about their plug-in hybrid cars are obviously far from the truth,” commented a automotive expert. “Buyers are being misled into believing that by buying a PHEV, they are helping the environment and saving money. Actually, PHEVs are little better than regular petrol and diesel vehicles in terms of energy use, CO₂ production, and operating expenses.”

Policy Debate and Automotive Lobbying

Plug-in hybrid cars have recently been brought back into policy discussions as automakers have pressed the European Union to relax CO₂ standards. A proposed ban on new combustion engine vehicles in 2035 has faced intense pressure from the car sector and resistance from member states with large automotive manufacturing.

Several senior officials have suggested plug-in hybrids as a potential “flexibility” option to include in the regulation.

One independent energy economics expert, who was not involved with the research, described the analysis a “highly valuable contribution” after a long period in which parts of the automotive industry claimed there was too little information to accurately assess real-world emissions.

“These findings demonstrate, without question, that the difference between lab and real-world PHEV energy use and CO₂ emissions is significantly greater than for gasoline or conventional vehicles,” they stated. “All policy changes regarding PHEVs should be implemented with utmost care and considering this evidence.”