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Plug-in hybrid cars produce almost 5x more planet-heating emissions than official figures indicate, as per a new analysis.

Widening Discrepancy In Lab and Real-World Emissions

Statistics shows that PHEVs release just 19% lower CO₂ than traditional gas and diesel cars, according to analysis carried out by a non-profit organization. This contrasts sharply with lab estimates, which suggested a 75% reduction in emissions.

Analysts examined information from onboard energy use monitors of 800,000 cars registered in Europe between 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported figures are decreasing,” said a senior analyst participating in the report. “That discrepancy is growing and creates a significant issue. As a result, PHEVs pollute almost as much as gasoline cars.”

Primary Factors Driving the Emissions Gap

Researchers attributed most of the gap to inflated estimates of the “electric driving share” – the ratio of miles driven in battery power relative to total distance. The team determined that only a quarter of driving was completed in electric mode, while official assumptions suggested 84%.

Even, when running in electric mode, emission amounts were well above lab projections. That happened because electric motors were insufficiently powerful sufficient to function independently, resulting to combustion motors burning gasoline for almost a third of the distance covered in electric mode.

Regulatory and Financial Consequences

Based on calculations, the underestimation of PHEV CO2 output enabled several large carmaker companies to escape more than €5bn in fines from 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ targets.

Furthermore, owners of PHEVs would pay about €500 extra annually in operating costs than is estimated under lab conditions.

“The bold claims that automakers like to make about their plug-in hybrid cars are obviously far from the mark,” commented a automotive expert. “Buyers are being misled into thinking that by buying a PHEV, they are helping the planet and cutting money. In reality, PHEVs are little improved than regular petrol and diesel cars in terms of fuel use, CO₂ production, and operating costs.”

Policy Discussion and Industry Lobbying

Plug-in hybrid cars have lately been drawn again into political debates as automakers have pressed the European Union to weaken CO₂ standards. A planned prohibition on sales of new combustion engine vehicles in 2035 has faced intense pressure from the automotive sector and opposition from member states with large car industries.

Some high-level officials have proposed PHEVs as a possible “flexibility” option to introduce in the regulation.

One independent energy policy specialist, who was unaffiliated with the research, called the report a “highly valuable addition” after years in which segments of the automotive sector argued there was insufficient data to properly evaluate real-world CO2 output.

“The results demonstrate, beyond any doubt, that the difference in official and real-world PHEV energy use and CO₂ output is much, much larger than for petrol or conventional vehicles,” they stated. “All regulatory adjustments regarding PHEVs should be implemented with utmost caution and in the light of this evidence.”