Plug-in Hybrid Vehicles Emit Almost as Much as Petrol Cars, Study Reveals

Plug-in hybrid cars produce almost 5x greater planet-heating pollution than official data show, according to a recent analysis.

Widening Discrepancy In Lab and Actual CO2 Output

Data shows that PHEVs emit just 19% less CO₂ than conventional petrol and diesel vehicles, based on analysis conducted by a advocacy group. This contrasts sharply with lab estimates, which assumed a three-quarters decrease in emissions.

Researchers examined data from in-vehicle energy use monitors of 800,000 cars sold in the EU from 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab figures, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official figures are decreasing,” stated a lead analyst participating in the report. “That gap is growing and creates a serious issue. Consequently, PHEVs emit nearly as much as gasoline cars.”

Primary Reasons Driving the Discrepancy

Researchers attributed the majority of the difference to inflated estimates of the “utility factor” – the ratio of kilometers travelled in battery mode compared to total mileage. The team determined that only 27% of travel was done in EV mode, whereas official estimates suggested over four-fifths.

Additionally, when operating in EV mode, emission levels were significantly higher than official estimates. This happened because electric motors were insufficiently powerful enough to function alone, resulting to combustion motors using fossil fuels for almost one-third of the travel completed in EV mode.

Policy and Economic Consequences

Based on estimates, the lowballing of PHEV CO2 output allowed four major automaker companies to avoid over €5bn in fines between 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs could pay about €500 more per year in operating expenses than would be assumed under laboratory conditions.

“The strong statements that automakers often promote about their PHEV cars are obviously far from the truth,” commented a transport analyst. “Buyers are being duped into believing that by buying a PHEV, they are helping the environment and saving costs. Actually, PHEVs are little improved than regular petrol and diesel cars in terms of energy use, CO₂ emissions, and operating costs.”

Political Discussion and Automotive Lobbying

Hybrid cars have recently been drawn back into policy debates as carmakers have pressed the EU to relax CO₂ targets. A proposed ban on sales of new internal combustion vehicles in 2035 has faced intense pressure from the automotive sector and resistance from EU countries with large automotive industries.

Some senior officials have suggested plug-in hybrids as a possible “flexibility” solution to include in the regulation.

One external energy economics expert, who was unaffiliated with the research, called the report a “highly valuable addition” after years in which parts of the car industry argued there was insufficient data to properly assess real-world emissions.

“The results show, without question, that the difference between official and actual PHEV energy use and CO₂ emissions is much, much larger than for petrol or conventional vehicles,” they stated. “All policy changes regarding PHEVs should be made with extreme caution and in the light of that data.”