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

Plug-in hybrid cars produce almost 5x more planet-heating emissions than lab-reported figures show, according to a recent report.

Widening Gap Between Lab and Actual CO2 Output

Statistics reveals that PHEVs emit only 19% lower CO₂ than conventional gas and diesel cars, according to research carried out by a non-profit organization. That differs sharply with lab estimates, which assumed a 75% reduction in emissions.

Researchers studied data from in-vehicle fuel consumption monitors of 800,000 cars sold in Europe from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, up from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported emissions are decreasing,” said a lead analyst participating in the report. “This discrepancy is growing and creates a serious issue. Consequently, PHEVs emit almost as heavily as petrol vehicles.”

Key Factors Driving the Discrepancy

Analysts attributed the majority of the difference to overestimates of the “utility factor” – the ratio of kilometers driven in battery mode relative to total mileage. They found that just 27% of driving was completed in EV mode, whereas lab estimates suggested 84%.

Additionally, when operating in EV mode, emission amounts were significantly higher than official projections. This happened because EV motors were insufficiently powerful enough to operate independently, leading to engines using fossil fuels for nearly one-third of the travel completed in electric mode.

Policy and Economic Implications

Based on estimates, the lowballing of PHEV emissions allowed several large carmaker groups to avoid more than €5bn in fines between 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ standards.

Additionally, owners of PHEVs would pay approximately €500 more per year in running expenses than is estimated under laboratory tests.

“The bold statements that manufacturers often promote about their plug-in hybrid vehicles are obviously way off the mark,” stated a transport analyst. “Consumers are being duped into believing that by buying a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are little better than regular gas and diesel vehicles in terms of energy use, CO₂ production, and running expenses.”

Policy Debate and Industry Lobbying

Plug-in hybrid cars have recently been brought again into policy discussions as carmakers have pressed the European Union to relax CO₂ targets. A planned prohibition on new internal combustion vehicles in 2035 has faced intense pressure from the automotive industry and resistance from member states with large car manufacturing.

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

One external energy economics expert, who was not involved with the research, described the report a “highly valuable addition” after a long period in which segments of the car industry claimed there was insufficient data to properly evaluate actual CO2 output.

“These findings show, without question, that the difference between official and real-world PHEV energy use and CO₂ output is much, much greater than for gasoline or diesel cars,” the expert stated. “All policy changes regarding PHEVs should be implemented with utmost care and in the light of this evidence.”