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Plug-in hybrid cars release nearly 5x greater global warming pollution than lab-reported data show, as per a recent analysis.

Growing Discrepancy Between Official and Real-World CO2 Output

Data shows that PHEVs emit only one-fifth less CO₂ than conventional petrol and diesel vehicles, according to research conducted by a non-profit organization. That differs significantly with laboratory tests, which suggested a 75% reduction in pollution.

Researchers examined data from in-vehicle fuel consumption monitors of 800,000 cars sold in the EU between 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than official estimates, up from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are decreasing,” said a lead analyst involved in the report. “This gap is growing and poses a serious problem. As a result, PHEVs emit nearly as heavily as gasoline vehicles.”

Primary Factors Driving the Discrepancy

Researchers linked the majority of the difference to overestimates of the “utility factor” – the percentage of kilometers travelled in electric power relative to total distance. They found that just 27% of driving was done in EV mode, whereas lab assumptions assumed over four-fifths.

Even, when operating in electric mode, pollution amounts were well above lab estimates. This happened because electric motors were insufficiently powerful enough to function alone, resulting to engines using gasoline for nearly one-third of the distance covered in EV mode.

Policy and Financial Consequences

Based on estimates, the lowballing of PHEV emissions enabled several major carmaker companies to escape more than €5bn in fines from 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs would spend about €500 more annually in running costs than is estimated under laboratory conditions.

“The bold statements that automakers like to make about their plug-in hybrid cars are clearly way off the truth,” commented a transport expert. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are little better than standard gas and diesel cars in terms of energy use, CO₂ emissions, and operating costs.”

Policy Debate and Automotive Lobbying

Hybrid cars have lately been drawn back into political discussions as automakers have lobbied the EU to weaken CO₂ standards. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the automotive industry and resistance from member states with significant car industries.

Some senior politicians have proposed plug-in hybrids as a possible “compromise” solution to introduce in the regulation.

An independent energy economics specialist, who was not involved with the research, described the report a “highly valuable addition” after years in which parts of the car industry claimed there was insufficient information to properly evaluate real-world CO2 output.

“The results demonstrate, without question, that the gap in lab and real-world PHEV energy use and CO₂ emissions is much, much greater than for gasoline or conventional vehicles,” they stated. “All regulatory adjustments concerning PHEVs should be implemented with utmost care and considering this evidence.”