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Plug-in hybrid electric vehicles release nearly five times greater global warming emissions than official figures show, as per a new analysis.

Growing Gap Between Lab and Actual CO2 Output

Statistics reveals that PHEVs emit only 19% less CO₂ than traditional petrol and diesel cars, based on analysis carried out by a non-profit group. That differs sharply with laboratory estimates, which suggested a 75% decrease in pollution.

Analysts studied data from onboard energy use monitors of eight hundred thousand cars registered in the EU from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are falling,” stated a senior analyst involved in the study. “That gap is growing and creates a significant issue. Consequently, PHEVs pollute almost as much as gasoline vehicles.”

Key Reasons Behind the Discrepancy

Analysts attributed most of the gap to overestimates of the “utility factor” – the ratio of miles travelled in electric mode relative to overall mileage. They found that just a quarter of driving was done in electric mode, whereas official estimates assumed 84%.

Additionally, when running in EV mode, pollution amounts were significantly higher than lab estimates. That occurred because electric motors were insufficiently powerful enough to operate independently, resulting to combustion motors using fossil fuels for almost a third of the travel completed in EV mode.

Regulatory and Financial Consequences

Based on estimates, the underestimation of PHEV emissions allowed four major automaker companies to avoid more than €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs could spend about €500 more annually in operating costs than would be assumed under lab tests.

“The strong claims that automakers like to make about their plug-in hybrid cars are obviously far from the truth,” commented a transport analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are little better than standard petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and operating costs.”

Policy Discussion and Automotive Pressure

Hybrid vehicles have lately been drawn again into policy discussions as carmakers have lobbied the European Union to relax CO₂ standards. A planned prohibition on sales of new combustion engine vehicles in 2035 has faced heavy lobbying from the car industry and opposition from member states with significant car manufacturing.

Several high-level officials have suggested plug-in hybrids as a possible “compromise” option to include in the legislation.

One independent energy economics specialist, who was not involved with the study, described the analysis a “highly valuable addition” after a long period in which segments of the car sector claimed there was too little information to properly evaluate real-world CO2 output.

“These findings demonstrate, without question, that the gap in official and real-world PHEV energy use and CO₂ output is significantly larger than for petrol or diesel vehicles,” the expert stated. “All policy changes regarding PHEVs should be implemented with utmost care and considering that data.”