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PHEVs release nearly 5x more planet-heating pollution than lab-reported data show, according to a new analysis.

Growing Gap Between Official and Real-World CO2 Output

Statistics reveals that PHEVs release only 19% lower CO₂ than traditional petrol and diesel vehicles, based on analysis conducted by a advocacy group. That contrasts sharply with laboratory tests, which suggested a three-quarters reduction in emissions.

Researchers studied information from onboard fuel consumption monitors of 800,000 vehicles sold in Europe between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, up from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported emissions are decreasing,” stated a senior researcher participating in the study. “That gap is widening and poses a serious problem. As a result, PHEVs emit nearly as much as gasoline cars.”

Key Factors Behind the Discrepancy

Researchers attributed the majority of the difference to inflated estimates of the “utility factor” – the ratio of kilometers driven in electric mode relative to overall distance. They determined that just a quarter of driving was done in EV mode, whereas lab assumptions assumed 84%.

Additionally, when operating in EV mode, pollution amounts were significantly higher than official estimates. This occurred because electric motors were insufficiently powerful sufficient to operate independently, resulting to combustion motors burning gasoline for nearly one-third of the distance completed in electric mode.

Regulatory and Financial Consequences

Based on calculations, the lowballing of PHEV emissions enabled several major automaker groups to avoid more than €5bn in penalties between 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs could spend about €500 more per year in operating costs than would be estimated under laboratory conditions.

“The strong statements that manufacturers often promote about their PHEV vehicles are obviously far from the truth,” commented a automotive analyst. “Buyers are being duped into believing that by buying a PHEV, they are helping the environment and cutting money. Actually, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of fuel consumption, CO₂ production, and operating costs.”

Political Debate and Automotive Pressure

Hybrid vehicles have recently been brought back into policy debates as carmakers have lobbied the EU to relax CO₂ targets. A proposed prohibition on new internal combustion cars in 2035 has faced heavy lobbying from the automotive sector and opposition from member states with large automotive industries.

Some high-level officials have suggested PHEVs as a potential “compromise” option to introduce in the legislation.

An independent energy economics expert, who was not involved with the study, described the report a “highly valuable addition” after years in which segments of the car sector claimed there was insufficient data to accurately evaluate actual emissions.

“These findings demonstrate, without question, that the difference in lab and real-world PHEV energy use and CO₂ output is much, much larger than for petrol or conventional cars,” they said. “Any regulatory adjustments concerning PHEVs should be made with extreme caution and in the light of this evidence.”