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Plug-in hybrid electric vehicles emit almost 5x more planet-heating pollution than lab-reported data indicate, as per a new analysis.

Growing Gap Between Official and Actual CO2 Output

Data reveals that PHEVs release just one-fifth less CO₂ than traditional petrol and diesel cars, according to analysis carried out by a non-profit group. That differs sharply with lab tests, which assumed a three-quarters decrease in pollution.

Analysts studied information from onboard energy use meters of 800,000 cars sold in Europe from 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, up from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported emissions are decreasing,” said a lead researcher involved in the report. “This discrepancy is growing and poses a significant issue. As a result, PHEVs emit almost as heavily as petrol cars.”

Primary Reasons Driving the Discrepancy

Analysts linked the majority of the difference to inflated estimates of the “electric driving share” – the percentage of kilometers driven in electric mode relative to overall distance. They found that just 27% of driving was completed in electric mode, while official assumptions assumed over four-fifths.

Even, when running in EV mode, pollution amounts were significantly higher than official estimates. That happened because EV motors were not strong sufficient to function alone, resulting to combustion motors burning fossil fuels for almost a third of the travel covered in electric mode.

Policy and Financial Consequences

Based on estimates, the lowballing of PHEV emissions enabled several large carmaker companies to escape over €5bn in fines from 2021 and 2023, by falsely simplifying compliance with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs would spend approximately €500 more annually in operating expenses than is estimated under laboratory tests.

“The strong claims that manufacturers often promote about their plug-in hybrid vehicles are obviously far from the truth,” stated a automotive analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are little better than regular petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and running costs.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid cars have lately been drawn back into policy debates as automakers have pressed the European Union to relax CO₂ targets. A proposed prohibition on new internal combustion cars in 2035 has faced intense pressure from the automotive sector and resistance from member states with large automotive industries.

Several high-level officials have proposed PHEVs as a potential “compromise” solution to include in the legislation.

An independent energy policy specialist, who was not involved with the study, called the report a “very useful contribution” after years in which parts of the automotive industry argued there was insufficient information to properly evaluate real-world emissions.

“The results demonstrate, beyond any doubt, that the gap between lab and actual PHEV energy use and CO₂ output is much, much larger than for gasoline or conventional cars,” they stated. “Any regulatory adjustments regarding PHEVs should be made with utmost care and in the light of this data.”