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PHEVs emit nearly 5x greater planet-heating pollution than official data indicate, according to a new analysis.

Growing Gap Between Lab and Real-World CO2 Output

Data shows that PHEVs emit just 19% less CO₂ than traditional gas and diesel cars, according to analysis carried out by a advocacy group. That contrasts sharply with laboratory estimates, which assumed a three-quarters reduction in pollution.

Analysts examined information from onboard fuel consumption monitors of eight hundred thousand vehicles sold in the EU between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official figures are falling,” said a lead researcher involved in the report. “That gap is widening and poses a serious issue. Consequently, PHEVs emit nearly as heavily as petrol cars.”

Key Factors Driving the Emissions Gap

Researchers attributed most of the gap to inflated estimates of the “utility factor” – the ratio of miles travelled in battery power compared to total mileage. The team found that just a quarter of travel was done in electric mode, whereas official estimates suggested 84%.

Additionally, when operating in EV mode, emission amounts were significantly higher than lab estimates. That occurred because electric motors were not strong sufficient to function alone, resulting to engines using fossil fuels for nearly one-third of the distance completed in EV mode.

Regulatory and Financial Implications

Based on calculations, the underestimation of PHEV emissions enabled several large carmaker companies to escape over €5bn in fines from 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs would pay approximately €500 more per year in running costs than would be estimated under laboratory tests.

“The strong claims that manufacturers like to make about their plug-in hybrid cars are obviously far from the mark,” commented a automotive expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are little improved than standard petrol and diesel cars in terms of energy use, CO₂ emissions, and operating costs.”

Political Discussion and Industry Pressure

Hybrid cars have recently been brought back into policy discussions as automakers have lobbied the European Union to relax CO₂ standards. A proposed ban on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the car sector and opposition from EU countries with significant automotive industries.

Some high-level officials have suggested PHEVs as a potential “flexibility” option to include in the regulation.

One independent energy economics expert, who was unaffiliated with the study, called the report a “highly valuable contribution” after years in which segments of the automotive industry claimed there was insufficient information to accurately evaluate actual emissions.

“The results show, beyond any doubt, that the difference in lab and actual PHEV energy use and CO₂ output is much, much greater than for gasoline or conventional vehicles,” they said. “Any regulatory adjustments regarding PHEVs should be implemented with extreme caution and considering this evidence.”