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Plug-in hybrid electric vehicles emit nearly five times more global warming pollution than lab-reported figures indicate, as per a new report.

Growing Discrepancy Between Lab and Real-World CO2 Output

Data shows that PHEVs emit just one-fifth less CO₂ than conventional gas and diesel cars, according to analysis conducted by a non-profit organization. That differs significantly with laboratory estimates, which assumed a three-quarters decrease in emissions.

Analysts examined information from onboard energy use monitors of eight hundred thousand cars sold in the EU between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are decreasing,” stated a senior analyst involved in the report. “That gap is widening and poses a significant issue. As a result, PHEVs pollute almost as heavily as petrol vehicles.”

Primary Reasons Behind the Discrepancy

Analysts linked the majority of the difference to inflated estimates of the “utility factor” – the percentage of kilometers driven in battery mode relative to overall distance. They found that just 27% of driving was done in electric mode, whereas official assumptions suggested over four-fifths.

Additionally, when running in EV mode, pollution amounts were well above lab estimates. This occurred because electric motors were not strong sufficient to function independently, resulting to combustion motors using fossil fuels for almost one-third of the travel completed in EV mode.

Regulatory and Economic Consequences

Based on estimates, the lowballing of PHEV CO2 output enabled four large carmaker groups to avoid over €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ targets.

Additionally, owners of PHEVs could pay approximately €500 extra per year in operating costs than is assumed under lab tests.

“The bold claims that manufacturers often promote about their plug-in hybrid cars are clearly way off the mark,” commented a transport analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are only slightly improved than standard petrol and diesel cars in terms of energy use, CO₂ emissions, and operating costs.”

Policy Debate and Automotive Pressure

Plug-in hybrid cars have lately been brought again into policy discussions as automakers have lobbied the European Union to relax CO₂ targets. A proposed prohibition on sales of new combustion engine vehicles in 2035 has faced intense pressure from the car industry and opposition from member states with significant car industries.

Some senior politicians have suggested PHEVs as a potential “compromise” option to introduce in the regulation.

One external energy policy expert, who was unaffiliated with the study, called the analysis a “highly valuable addition” after years in which segments of the car sector claimed there was insufficient information to accurately evaluate real-world CO2 output.

“The results demonstrate, without question, that the gap in lab and real-world PHEV energy use and CO₂ output is significantly greater than for petrol or conventional cars,” the expert said. “Any policy adjustments concerning PHEVs should be implemented with extreme caution and in the light of that data.”