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PHEVs produce nearly five times greater global warming pollution than official data indicate, according to a recent analysis.

Widening Gap In Lab and Real-World CO2 Output

Statistics shows that PHEVs release only 19% less CO₂ than traditional gas and diesel cars, based on analysis conducted by a non-profit organization. That differs sharply with laboratory tests, which suggested a 75% reduction in emissions.

Analysts examined information from in-vehicle energy use monitors of 800,000 cars sold in the EU from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, up from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported figures are decreasing,” stated a senior researcher participating in the study. “This discrepancy is widening and creates a significant problem. Consequently, PHEVs emit nearly as heavily as petrol vehicles.”

Primary Factors Driving the Discrepancy

Analysts attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in battery power relative to overall distance. They found that only 27% of travel was completed in EV mode, whereas official assumptions assumed over four-fifths.

Additionally, when running in electric mode, pollution amounts were significantly higher than lab projections. That happened because electric motors were insufficiently powerful sufficient to function independently, leading to combustion motors using gasoline for nearly a third of the travel completed in EV mode.

Regulatory and Financial Consequences

According to estimates, the underestimation of PHEV CO2 output allowed four major automaker groups to avoid more than €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could spend approximately €500 more per year in running costs than would be estimated under laboratory conditions.

“The strong claims that automakers like to make about their PHEV cars are obviously far from the mark,” stated a transport analyst. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are only slightly improved than regular petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and operating expenses.”

Policy Discussion and Industry Lobbying

Hybrid cars have recently been brought back into political debates as automakers have lobbied the European Union to relax CO₂ targets. A planned ban on sales of new combustion engine cars in 2035 has faced intense pressure from the automotive industry and opposition from member states with large automotive manufacturing.

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

An independent energy policy expert, who was unaffiliated with the research, described the analysis a “very useful contribution” after a long period in which parts of the automotive sector argued there was too little data to accurately assess actual CO2 output.

“These findings demonstrate, without question, that the difference between lab and real-world PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or conventional cars,” the expert said. “Any regulatory adjustments concerning PHEVs should be implemented with utmost caution and considering this data.”