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PHEVs release almost 5x more planet-heating pollution than lab-reported data indicate, according to a recent analysis.

Growing Discrepancy Between Lab and Actual CO2 Output

Statistics reveals that PHEVs release just 19% lower CO₂ than traditional petrol and diesel vehicles, according to analysis carried out by a non-profit group. This contrasts sharply with lab tests, which assumed a 75% reduction in emissions.

Researchers examined information from onboard energy use monitors of 800,000 cars registered in Europe from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times greater than official estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while official emissions are decreasing,” said a lead researcher involved in the report. “This discrepancy is widening and creates a serious issue. Consequently, PHEVs pollute almost as much as gasoline vehicles.”

Key Factors Behind the Discrepancy

Analysts attributed most of the difference to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in battery mode relative to total distance. They determined that only a quarter of travel was done in electric mode, while official estimates suggested over four-fifths.

Even, when operating in electric mode, emission levels were significantly higher than lab projections. That happened because EV motors were not strong sufficient to function independently, resulting to combustion motors using gasoline for nearly a third of the travel covered in EV mode.

Policy and Financial Consequences

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

Furthermore, owners of PHEVs could pay approximately €500 more annually in running expenses than would be assumed under lab tests.

“The bold statements that automakers like to make about their plug-in hybrid cars are obviously way off the truth,” commented a automotive expert. “Buyers are being duped into believing that by buying a PHEV, they are helping the planet and cutting money. Actually, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating costs.”

Policy Debate and Automotive Lobbying

Plug-in hybrid cars have lately been brought back into political discussions as carmakers have pressed the EU to relax CO₂ standards. A planned prohibition on new combustion engine vehicles in 2035 has faced intense lobbying from the car sector and resistance from EU countries with significant automotive industries.

Several high-level officials have suggested plug-in hybrids as a possible “compromise” solution to include in the regulation.

An independent energy policy specialist, who was unaffiliated with the research, called the analysis a “highly valuable addition” after years in which segments of the car industry claimed there was insufficient data to properly assess real-world emissions.

“These findings show, without question, that the difference in official and real-world PHEV energy use and CO₂ emissions is much, much greater than for gasoline or conventional cars,” they stated. “All policy changes concerning PHEVs should be implemented with extreme caution and in the light of this data.”