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Plug-in hybrid electric vehicles release almost 5x more global warming emissions than lab-reported data indicate, according to a recent report.

Widening Discrepancy In Lab and Real-World Emissions

Data shows that PHEVs emit just 19% lower CO₂ than traditional gas and diesel vehicles, based on research conducted by a advocacy organization. That contrasts sharply with lab estimates, which suggested a 75% reduction in emissions.

Researchers studied information from onboard fuel consumption monitors of eight hundred thousand vehicles sold in Europe from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, up from three and a half times in 2021.

“Actual emissions are increasing, while official figures are decreasing,” said a senior analyst participating in the report. “This gap is widening and poses a serious issue. Consequently, PHEVs pollute almost as much as petrol cars.”

Key Reasons Driving the Discrepancy

Analysts attributed most of the gap to inflated estimates of the “utility factor” – the percentage of kilometers travelled in battery mode relative to total distance. The team determined that just a quarter of driving was done in EV mode, whereas lab assumptions suggested over four-fifths.

Even, when running in electric mode, pollution levels were significantly higher than official projections. This happened because electric motors were insufficiently powerful enough to operate alone, leading to engines burning fossil fuels for almost one-third of the distance completed in electric mode.

Policy and Financial Consequences

According to estimates, the lowballing of PHEV CO2 output allowed four major automaker companies to escape more than €5bn in fines from 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ targets.

Furthermore, drivers of PHEVs could pay about €500 extra per year in operating costs than is assumed under lab tests.

“The strong statements that manufacturers like to make about their plug-in hybrid vehicles are clearly way off the mark,” commented a automotive expert. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the environment and cutting money. In reality, PHEVs are only slightly improved than regular gas and diesel vehicles in terms of fuel consumption, CO₂ production, and operating expenses.”

Policy Debate and Industry Pressure

Plug-in hybrid vehicles have recently been drawn back into political debates as automakers have pressed the EU to relax CO₂ targets. A proposed ban on new internal combustion vehicles in 2035 has faced heavy lobbying from the car industry and resistance from EU countries with significant car manufacturing.

Some senior officials have proposed plug-in hybrids as a potential “flexibility” option to include in the legislation.

An independent energy economics expert, who was not involved with the study, called the report a “very useful addition” after a long period in which segments of the automotive sector claimed there was insufficient data to properly evaluate real-world CO2 output.

“The results demonstrate, without question, that the difference in official and actual PHEV fuel consumption and CO₂ emissions is significantly greater than for petrol or diesel cars,” the expert stated. “All policy changes regarding PHEVs should be implemented with utmost caution and in the light of this evidence.”