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Plug-in hybrid cars release nearly five times greater global warming pollution than official figures show, according to a new report.

Widening Gap In Official and Actual CO2 Output

Statistics reveals that PHEVs emit just one-fifth lower CO₂ than conventional gas and diesel cars, according to analysis conducted by a non-profit organization. This differs sharply with laboratory estimates, which suggested a three-quarters reduction in pollution.

Researchers studied data from in-vehicle energy use meters of 800,000 cars registered in Europe between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official estimates, up from three and a half times in 2021.

“Real-world emissions are increasing, while official figures are falling,” stated a lead researcher involved in the study. “This gap is widening and poses a serious issue. Consequently, PHEVs pollute almost as heavily as petrol cars.”

Primary Factors Driving the Emissions Gap

Analysts attributed most of the difference to inflated estimates of the “utility factor” – the percentage of kilometers driven in battery mode relative to total mileage. The team determined that just a quarter of travel was done in electric mode, while lab estimates assumed over four-fifths.

Additionally, when running in electric mode, pollution amounts were well above official projections. That happened because EV motors were not strong sufficient to function independently, resulting to combustion motors burning fossil fuels for almost one-third of the distance completed in electric mode.

Policy and Economic Implications

Based on calculations, the lowballing of PHEV CO2 output 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.

Furthermore, owners of PHEVs would pay approximately €500 extra per year in running costs than is estimated under lab conditions.

“The bold statements that manufacturers often promote about their plug-in hybrid vehicles are obviously far from the truth,” commented a transport expert. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are only slightly improved than regular petrol and diesel cars in terms of energy consumption, CO₂ emissions, and operating expenses.”

Policy Discussion and Automotive Pressure

Hybrid vehicles have lately been drawn back into policy debates as carmakers have lobbied the EU to weaken CO₂ standards. A planned ban on sales of new internal combustion vehicles in 2035 has faced intense pressure from the automotive industry and resistance from member states with large car industries.

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

One external energy economics specialist, who was not involved with the study, described the report a “very useful addition” after a long period in which parts of the car sector claimed there was insufficient information to properly assess actual CO2 output.

“The results show, without question, that the difference in official and actual PHEV energy use and CO₂ emissions is much, much greater than for petrol or conventional vehicles,” they said. “Any regulatory changes regarding PHEVs should be implemented with utmost caution and considering that data.”