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Plug-in hybrid cars release nearly five times more global warming pollution than official data show, according to a recent analysis.

Growing Discrepancy In Lab and Real-World Emissions

Data shows that PHEVs emit just one-fifth lower CO₂ than conventional gas and diesel vehicles, according to analysis conducted by a non-profit group. That differs sharply with lab estimates, which assumed a 75% decrease in emissions.

Analysts examined information from onboard fuel consumption monitors of 800,000 vehicles sold in the EU from 2021 and 2023. The team found that actual CO₂ emissions 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 falling,” stated a lead researcher involved in the report. “That gap is widening and creates a serious issue. As a result, PHEVs pollute almost as much as gasoline cars.”

Primary Factors Driving the Discrepancy

Analysts linked most of the difference to inflated estimates of the “electric driving share” – the percentage of miles driven in electric mode compared to overall distance. They found that just 27% of travel was completed in EV mode, while official estimates assumed over four-fifths.

Additionally, when running in EV mode, pollution levels were well above lab estimates. This happened because EV motors were insufficiently powerful sufficient to function alone, resulting to engines using fossil fuels for nearly a third of the travel completed in EV mode.

Policy and Financial Implications

According to calculations, the lowballing of PHEV emissions allowed several major automaker groups to escape over €5bn in penalties between 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ standards.

Furthermore, drivers of PHEVs would spend about €500 extra per year in running expenses than would be assumed under laboratory conditions.

“The bold claims that manufacturers often promote about their PHEV vehicles are obviously far from the mark,” stated a transport analyst. “Buyers are being duped into believing that by buying a PHEV, they are helping the planet and saving money. Actually, PHEVs are little improved than standard petrol and diesel cars in terms of energy use, CO₂ production, and running costs.”

Political Discussion and Automotive Lobbying

Plug-in hybrid cars have recently been drawn again into political discussions as carmakers have pressed the European Union to weaken CO₂ targets. A planned prohibition on sales of new combustion engine cars in 2035 has faced heavy lobbying from the automotive industry and opposition from member states with large car industries.

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

An independent energy economics expert, who was not involved with the study, called the analysis a “very useful addition” after a long period in which parts of the automotive sector argued there was too little data to properly assess actual CO2 output.

“These findings show, without question, that the gap in lab and real-world PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or conventional cars,” they stated. “Any regulatory changes concerning PHEVs should be made with extreme care and in the light of this evidence.”