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Plug-in hybrid electric vehicles release almost 5x greater planet-heating emissions than lab-reported figures indicate, according to a new analysis.

Widening Discrepancy In Lab and Real-World CO2 Output

Data shows that PHEVs emit just one-fifth less CO₂ than traditional gas and diesel cars, according to analysis conducted by a non-profit group. That contrasts significantly with lab estimates, which suggested a three-quarters decrease in emissions.

Analysts examined information from onboard fuel consumption monitors of 800,000 cars registered in Europe from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, increased from three and a half times in 2021.

“Actual emissions are rising, while official emissions are decreasing,” stated a lead analyst involved in the study. “This discrepancy is growing and poses a significant issue. Consequently, PHEVs emit nearly as heavily as gasoline cars.”

Primary Factors Driving the Discrepancy

Analysts attributed most of the gap to inflated estimates of the “utility factor” – the percentage of miles driven in electric power relative to total distance. The team determined that just a quarter of travel was done in electric mode, whereas official estimates suggested 84%.

Additionally, when running in electric mode, emission amounts were well above official projections. This occurred because electric motors were insufficiently powerful sufficient to operate alone, resulting to engines using gasoline for almost a third of the distance covered in EV mode.

Regulatory and Financial Consequences

According to estimates, the underestimation of PHEV CO2 output allowed four major automaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs would spend about €500 extra per year in operating expenses than would be estimated under laboratory tests.

“The bold statements that manufacturers often promote about their plug-in hybrid cars are obviously way off the mark,” stated a transport expert. “Consumers are being misled into thinking that by buying a PHEV, they are helping the planet and cutting costs. In reality, PHEVs are little improved than regular petrol and diesel vehicles in terms of fuel consumption, CO₂ production, and operating costs.”

Policy Debate and Automotive Lobbying

Hybrid vehicles have lately been drawn back into political debates as automakers have pressed the European Union to weaken CO₂ standards. A planned ban on sales of new internal combustion vehicles in 2035 has faced intense pressure from the automotive industry and opposition from member states with large car manufacturing.

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

One independent energy economics specialist, who was not involved with the study, called the analysis a “very useful contribution” after years in which parts of the automotive sector claimed there was insufficient data to properly evaluate actual emissions.

“The results show, without question, that the gap in lab and real-world PHEV energy use and CO₂ emissions is significantly larger than for petrol or diesel cars,” they said. “All regulatory adjustments concerning PHEVs should be implemented with extreme care and in the light of that evidence.”