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Plug-in hybrid cars produce nearly five times greater global warming emissions than official data show, as per a new report.

Widening Gap Between Lab and Actual CO2 Output

Statistics reveals that PHEVs release just 19% less CO₂ than traditional gas and diesel vehicles, based on research conducted by a advocacy group. This differs significantly with lab tests, which assumed a 75% decrease in emissions.

Analysts studied information from onboard energy use meters of 800,000 cars registered in the EU between 2021 and 2023. They found that real-world CO₂ output 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 official emissions are falling,” said a senior analyst participating in the report. “That gap is widening and creates a serious problem. Consequently, PHEVs pollute nearly as much as gasoline cars.”

Key Reasons Driving the Discrepancy

Researchers attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in battery mode compared to total distance. They found that just 27% of travel was done in electric mode, while lab assumptions suggested 84%.

Additionally, when running in EV mode, emission amounts were significantly higher than official projections. This occurred because electric motors were insufficiently powerful enough to function independently, resulting to engines burning gasoline for nearly one-third of the distance completed in EV mode.

Regulatory and Financial Implications

According to calculations, the underestimation of PHEV CO2 output enabled several large carmaker companies to escape more than €5bn in fines between 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs would pay approximately €500 extra annually in running costs than would be assumed under lab conditions.

“The bold claims that automakers often promote about their plug-in hybrid cars are clearly way off the mark,” commented a transport analyst. “Buyers are being duped into thinking that by buying a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of energy use, CO₂ production, and operating expenses.”

Policy Debate and Industry Pressure

Plug-in hybrid vehicles have lately been drawn back into policy debates as automakers have lobbied the European Union to weaken CO₂ targets. A planned ban on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the car industry and resistance from EU countries with large car manufacturing.

Some senior politicians have proposed PHEVs as a potential “flexibility” option to include in the regulation.

An independent energy economics expert, who was not involved with the study, called the analysis a “very useful contribution” after a long period in which parts of the car sector claimed there was insufficient information to properly evaluate actual emissions.

“These findings show, without question, that the gap between official and actual PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or diesel vehicles,” the expert said. “All regulatory changes concerning PHEVs should be made with extreme care and in the light of that data.”