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Plug-in hybrid cars release almost five times more global warming emissions than lab-reported data indicate, as per a new report.

Widening Gap In Official and Actual Emissions

Statistics reveals that PHEVs emit only one-fifth less CO₂ than traditional gas and diesel cars, based on research conducted by a non-profit organization. That contrasts sharply with laboratory estimates, which assumed a 75% reduction in pollution.

Analysts studied data from in-vehicle energy use monitors of 800,000 cars registered in Europe between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, increased from three and a half times in 2021.

“Actual emissions are increasing, while official figures are decreasing,” stated a lead researcher participating in the report. “That gap is growing and creates a serious issue. As a result, PHEVs emit nearly as heavily as gasoline cars.”

Primary Factors Driving the Emissions Gap

Analysts linked the majority of the gap to overestimates of the “utility factor” – the percentage of kilometers driven in electric power relative to overall distance. The team determined that only a quarter of travel was completed in EV mode, while lab estimates assumed 84%.

Additionally, when running in electric mode, pollution levels were significantly higher than official projections. This happened because electric motors were insufficiently powerful enough to operate independently, leading to engines burning fossil fuels for almost a third of the travel completed in EV mode.

Regulatory and Financial Consequences

According to estimates, the underestimation of PHEV emissions enabled four large automaker groups to avoid more than €5bn in fines between 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs would pay about €500 extra per year in operating expenses than is estimated under lab tests.

“The bold statements that manufacturers often promote about their PHEV cars are obviously far from the truth,” commented a automotive analyst. “Consumers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and cutting costs. In reality, PHEVs are little improved than regular gas and diesel cars in terms of energy consumption, CO₂ emissions, and running expenses.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid cars have recently been brought back into political debates as carmakers have pressed the European Union to relax CO₂ targets. A proposed prohibition on sales of new combustion engine cars in 2035 has faced intense lobbying from the automotive sector and opposition from EU countries with large car industries.

Several high-level politicians have proposed PHEVs as a possible “flexibility” solution to include in the regulation.

An independent energy policy specialist, who was not involved with the research, described the report a “very useful contribution” after years in which parts of the car sector argued there was insufficient information to properly evaluate real-world CO2 output.

“These findings show, without question, that the gap between lab and actual PHEV fuel consumption and CO₂ output is much, much greater than for gasoline or diesel vehicles,” the expert stated. “All regulatory adjustments concerning PHEVs should be made with extreme caution and in the light of that evidence.”