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

Growing Discrepancy Between Lab and Actual CO2 Output

Data shows that PHEVs emit just 19% less CO₂ than traditional gas and diesel cars, based on analysis carried out by a advocacy organization. That contrasts sharply with laboratory tests, which assumed a 75% decrease in pollution.

Researchers studied information from in-vehicle fuel consumption monitors of 800,000 cars sold in Europe from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while official figures are decreasing,” stated a lead researcher participating in the report. “That discrepancy is growing and creates a significant issue. As a result, PHEVs pollute almost as heavily as gasoline cars.”

Primary Reasons Behind the Emissions Gap

Researchers linked most of the difference to overestimates of the “utility factor” – the percentage of kilometers travelled in battery mode relative to overall mileage. They found that just 27% of travel was completed in electric mode, while lab assumptions assumed 84%.

Additionally, when operating in electric mode, emission levels were well above official projections. That occurred because EV motors were insufficiently powerful sufficient to operate independently, resulting to engines burning fossil fuels for nearly one-third of the travel covered in electric mode.

Policy and Financial Consequences

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

Additionally, owners of PHEVs would pay approximately €500 extra annually in operating expenses than is estimated under laboratory tests.

“The bold statements that automakers like to make about their plug-in hybrid cars are clearly way off the mark,” commented a transport expert. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are little better than standard petrol and diesel cars in terms of fuel consumption, CO₂ production, and operating costs.”

Policy Debate and Automotive Lobbying

Hybrid vehicles have lately been brought back into policy debates as carmakers have lobbied the EU to weaken CO₂ standards. A planned ban on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the automotive sector and opposition from member states with significant automotive manufacturing.

Several senior politicians have suggested plug-in hybrids as a possible “compromise” solution to introduce in the legislation.

An external energy economics expert, who was not involved with the research, called the report a “highly valuable addition” after a long period in which parts of the automotive industry argued there was insufficient data to accurately assess actual emissions.

“These findings show, without question, that the difference in lab and actual PHEV energy use and CO₂ emissions is much, much larger than for gasoline or conventional cars,” they stated. “All policy adjustments regarding PHEVs should be implemented with utmost care and in the light of this data.”