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PHEVs produce almost five times more planet-heating pollution than official figures indicate, according to a recent analysis.

Growing Discrepancy Between Official and Real-World CO2 Output

Data reveals that PHEVs emit just one-fifth lower CO₂ than traditional gas and diesel cars, based on analysis conducted by a advocacy organization. That contrasts sharply with laboratory tests, which assumed a three-quarters reduction in pollution.

Researchers examined data from in-vehicle energy use monitors of 800,000 vehicles registered in Europe from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, up from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported figures are falling,” said a lead researcher participating in the study. “That gap is growing and poses a significant issue. Consequently, PHEVs pollute almost as heavily as gasoline vehicles.”

Key Reasons Driving the Discrepancy

Analysts linked the majority of the gap to overestimates of the “utility factor” – the ratio of miles driven in electric mode compared to overall distance. They found that only 27% of driving was completed in electric mode, whereas lab estimates suggested over four-fifths.

Even, when operating in EV mode, pollution levels were well above official projections. This occurred because EV motors were insufficiently powerful enough to operate alone, leading to engines burning fossil fuels for nearly one-third of the travel completed in electric mode.

Policy and Economic Consequences

According to calculations, the underestimation of PHEV emissions allowed several major automaker groups to avoid more than €5bn in fines between 2021 and 2023, by artificially easing adherence with EU average fleet CO₂ standards.

Additionally, owners of PHEVs could spend about €500 more annually in running expenses than is assumed under lab tests.

“The bold statements that automakers often promote about their plug-in hybrid cars are obviously far from the truth,” commented a automotive expert. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the environment and cutting costs. In reality, PHEVs are little improved than regular petrol and diesel vehicles in terms of fuel use, CO₂ production, and operating expenses.”

Policy Debate and Automotive Pressure

Hybrid vehicles have recently been brought again into policy debates as automakers have lobbied the EU to weaken CO₂ targets. A proposed ban on sales of new internal combustion cars in 2035 has faced intense pressure from the car industry and resistance from EU countries with large automotive manufacturing.

Several high-level officials have suggested PHEVs as a potential “flexibility” option to include in the regulation.

One external energy policy expert, who was not involved with the research, called the analysis a “highly valuable contribution” after years in which parts of the car industry claimed there was insufficient data to properly assess real-world emissions.

“These findings demonstrate, without question, that the difference between official and real-world PHEV fuel consumption and CO₂ emissions is significantly larger than for petrol or conventional vehicles,” they stated. “Any regulatory adjustments regarding PHEVs should be made with extreme care and considering this data.”