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Plug-in hybrid electric vehicles release nearly five times more planet-heating emissions than lab-reported figures indicate, according to a recent analysis.

Widening Gap Between Lab and Real-World CO2 Output

Statistics shows that PHEVs emit just one-fifth less CO₂ than traditional petrol and diesel vehicles, according to analysis carried out by a advocacy organization. That differs sharply with lab tests, which suggested a 75% decrease in pollution.

Analysts studied data from in-vehicle energy use meters of 800,000 cars registered in the EU between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official figures are decreasing,” said a lead analyst involved in the study. “This discrepancy is growing and creates a serious issue. Consequently, PHEVs pollute nearly as heavily as petrol vehicles.”

Key Reasons Behind the Emissions Gap

Analysts attributed most of the gap to overestimates of the “utility factor” – the percentage of miles driven in electric mode compared to total distance. They found that just a quarter of travel was done in electric mode, whereas official estimates assumed over four-fifths.

Even, when operating in electric mode, pollution amounts were well above official projections. This happened because electric motors were insufficiently powerful sufficient to function alone, resulting to engines using fossil fuels for almost one-third of the distance covered in EV mode.

Policy and Financial Consequences

According to calculations, the underestimation of PHEV CO2 output allowed several large carmaker groups to escape over €5bn in fines from 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ targets.

Additionally, owners of PHEVs would pay about €500 extra annually in running costs than would be assumed under laboratory tests.

“The bold statements that manufacturers like to make about their plug-in hybrid cars are clearly far from the mark,” stated a transport expert. “Buyers are being misled into thinking that by buying a PHEV, they are helping the environment and saving money. In reality, PHEVs are only slightly better than regular petrol and diesel cars in terms of energy consumption, CO₂ production, and operating costs.”

Policy Discussion and Automotive Pressure

Plug-in hybrid vehicles have lately been brought back into policy debates as automakers have pressed the EU to weaken CO₂ targets. A proposed ban on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the automotive industry and opposition from member states with significant automotive manufacturing.

Some senior officials have suggested PHEVs as a potential “compromise” option to include in the legislation.

An independent energy economics expert, who was not involved with the study, described the report a “very useful contribution” after years in which segments of the car sector claimed there was too little data to accurately evaluate real-world emissions.

“The results demonstrate, beyond any doubt, that the difference between lab and real-world PHEV fuel consumption and CO₂ output is significantly greater than for petrol or conventional vehicles,” they stated. “All regulatory adjustments regarding PHEVs should be implemented with extreme caution and considering this evidence.”