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Plug-in hybrid cars emit almost 5x greater global warming emissions than official data indicate, as per a recent report.

Growing Gap In Official and Real-World Emissions

Data reveals that PHEVs emit just 19% less CO₂ than traditional petrol and diesel vehicles, based on analysis carried out by a non-profit group. This differs sharply with lab tests, which suggested a three-quarters reduction in pollution.

Analysts studied data from in-vehicle fuel consumption monitors of 800,000 vehicles sold in Europe from 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab estimates, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are decreasing,” stated a lead analyst participating in the report. “This gap is widening and poses a serious problem. As a result, PHEVs pollute nearly as heavily as petrol vehicles.”

Primary Factors Driving the Emissions Gap

Researchers linked the majority of the difference to inflated estimates of the “utility factor” – the ratio of miles travelled in electric mode relative to overall distance. They determined that only a quarter of driving was completed in EV mode, whereas lab estimates suggested 84%.

Even, when running in EV mode, pollution levels were well above lab estimates. This happened because EV motors were not strong sufficient to operate alone, resulting to engines using gasoline for almost a third of the travel completed in electric mode.

Policy and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output allowed several large automaker companies to avoid more than €5bn in fines between 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs could spend about €500 more annually in operating costs than is assumed under laboratory conditions.

“The strong statements that manufacturers often promote about their plug-in hybrid vehicles are obviously far from the truth,” stated a transport expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of fuel use, CO₂ production, and running expenses.”

Policy Debate and Automotive Pressure

Plug-in hybrid cars have recently been drawn again into political discussions as automakers have lobbied the European Union to relax CO₂ targets. A planned prohibition on new internal combustion cars in 2035 has faced heavy lobbying from the automotive industry and opposition from member states with significant car manufacturing.

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

One external energy economics specialist, who was unaffiliated with the research, called the report a “very useful contribution” after years in which segments of the car industry argued there was too little data to accurately assess real-world CO2 output.

“These findings demonstrate, without question, that the gap between lab and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or conventional vehicles,” they stated. “All policy adjustments concerning PHEVs should be made with utmost caution and considering this evidence.”