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Plug-in hybrid cars produce nearly 5x more global warming emissions than official figures show, according to a new analysis.

Widening Discrepancy In Lab and Actual Emissions

Statistics reveals that PHEVs emit only one-fifth less CO₂ than traditional petrol and diesel cars, according to analysis carried out by a non-profit group. This contrasts sharply with laboratory tests, which assumed a three-quarters reduction in emissions.

Researchers examined information from in-vehicle fuel consumption monitors of eight hundred thousand cars registered in Europe between 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, up from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported emissions are decreasing,” stated a senior analyst participating in the report. “This gap is growing and poses a serious issue. As a result, PHEVs pollute nearly as heavily as gasoline vehicles.”

Key Reasons Behind the Discrepancy

Analysts attributed the majority of the gap to inflated estimates of the “electric driving share” – the ratio of miles travelled in battery mode compared to overall distance. The team found that just 27% of travel was done in EV mode, while official assumptions suggested over four-fifths.

Even, when running in electric mode, emission amounts were well above official projections. That occurred because electric motors were not strong sufficient to operate independently, leading to engines burning fossil fuels for almost a third of the distance covered in EV mode.

Regulatory and Economic Consequences

According to calculations, the lowballing of PHEV CO2 output allowed several large carmaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ standards.

Furthermore, drivers of PHEVs could pay about €500 more per year in running expenses than would be assumed under laboratory tests.

“The strong claims that automakers often promote about their plug-in hybrid vehicles are clearly far from the truth,” stated a transport analyst. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are little improved than standard gas and diesel vehicles in terms of energy consumption, CO₂ production, and running costs.”

Political Debate and Automotive Pressure

Plug-in hybrid vehicles have recently been drawn again into political debates as carmakers have pressed the European Union to relax CO₂ standards. A proposed prohibition on new internal combustion cars in 2035 has faced heavy pressure from the car sector and opposition from member states with large automotive industries.

Some high-level politicians have proposed plug-in hybrids as a potential “compromise” solution to introduce in the legislation.

An external energy policy expert, who was unaffiliated with the research, called the analysis a “highly valuable contribution” after a long period in which parts of the car sector claimed there was insufficient data to accurately assess actual emissions.

“These findings show, without question, that the difference between official and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or conventional cars,” the expert stated. “Any policy changes regarding PHEVs should be made with extreme caution and in the light of this data.”