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Plug-in hybrid cars emit nearly five times greater global warming pollution than official data show, as per a recent analysis.

Widening Gap Between Official and Actual CO2 Output

Data shows that PHEVs release just one-fifth less CO₂ than traditional petrol and diesel vehicles, based on research conducted by a non-profit group. That differs sharply with laboratory tests, which suggested a 75% decrease in pollution.

Analysts studied information from in-vehicle energy use meters of 800,000 vehicles registered in Europe between 2021 and 2023. The team discovered that actual CO₂ emissions 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 falling,” stated a lead researcher involved in the study. “This gap is widening and creates a significant issue. Consequently, PHEVs pollute nearly as heavily as gasoline vehicles.”

Primary Reasons Driving the Discrepancy

Researchers attributed most of the gap to overestimates of the “electric driving share” – the percentage of miles travelled in electric mode relative to total distance. They determined that just a quarter of driving was done in electric mode, whereas official assumptions suggested 84%.

Additionally, when operating in EV mode, emission levels were well above official projections. This occurred because EV motors were not strong sufficient to function alone, leading to engines burning gasoline for nearly one-third of the travel completed in electric mode.

Policy and Economic Consequences

According to calculations, the lowballing of PHEV emissions allowed four large carmaker companies to escape over €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs would pay about €500 more annually in operating costs than is assumed under laboratory conditions.

“The bold statements that automakers like to make about their plug-in hybrid vehicles are clearly way off the truth,” stated a automotive expert. “Buyers are being misled into believing that by buying a PHEV, they are helping the environment and saving money. Actually, PHEVs are only slightly better than regular gas and diesel vehicles in terms of energy consumption, CO₂ production, and operating costs.”

Policy Discussion and Automotive Pressure

Hybrid vehicles have recently been brought again into political discussions as carmakers have lobbied the European Union to weaken CO₂ standards. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the automotive industry and opposition from EU countries with large car industries.

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

One external energy policy expert, who was not involved with the study, called the analysis a “very useful contribution” after a long period in which parts of the automotive industry claimed there was too little information to properly evaluate actual emissions.

“The results show, without question, that the gap between official and actual PHEV energy use and CO₂ emissions is much, much greater than for petrol or diesel cars,” the expert said. “All regulatory adjustments concerning PHEVs should be implemented with extreme care and in the light of that evidence.”