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Plug-in hybrid cars emit nearly five times more global warming pollution than official figures show, as per a new analysis.

Widening Discrepancy Between Lab and Real-World Emissions

Statistics reveals that PHEVs release only 19% less CO₂ than conventional gas and diesel vehicles, based on analysis conducted by a non-profit group. That differs significantly with lab tests, which suggested a three-quarters decrease in pollution.

Analysts examined information from onboard energy use meters of eight hundred thousand cars sold in Europe from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, increased from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported figures are falling,” said a senior researcher participating in the report. “This discrepancy is widening and poses a significant problem. Consequently, PHEVs emit almost as heavily as gasoline vehicles.”

Primary Factors Driving the Emissions Gap

Analysts attributed the majority of the difference to inflated estimates of the “utility factor” – the percentage of kilometers driven in battery mode relative to overall distance. The team found that only 27% of driving was done in EV mode, whereas lab assumptions suggested over four-fifths.

Additionally, when operating in electric mode, emission levels were well above lab estimates. This happened because EV motors were insufficiently powerful sufficient to function alone, leading to combustion motors burning fossil fuels for nearly a third of the travel completed in electric mode.

Regulatory and Financial Implications

Based on estimates, the underestimation of PHEV emissions allowed four major carmaker companies to escape more than €5bn in fines from 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could spend about €500 extra per year in operating costs than is assumed under laboratory conditions.

“The strong claims that automakers like to make about their plug-in hybrid vehicles are obviously far from the truth,” stated a transport analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and saving money. In reality, PHEVs are little improved than regular gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and operating costs.”

Political Discussion and Industry Pressure

Hybrid cars have lately been brought again into political debates as automakers have lobbied the European Union to relax CO₂ standards. A planned prohibition on new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive sector and resistance from member states with large automotive industries.

Several senior officials have suggested plug-in hybrids as a possible “compromise” option to introduce in the regulation.

An external energy policy expert, who was not involved with the research, described the analysis a “very useful contribution” after a long period in which segments of the car sector argued there was too little data to properly assess real-world CO2 output.

“The results show, without question, that the difference between official and actual PHEV energy use and CO₂ emissions is significantly greater than for gasoline or conventional vehicles,” the expert said. “All policy changes regarding PHEVs should be implemented with utmost caution and in the light of this evidence.”