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Plug-in hybrid cars produce nearly 5x more planet-heating emissions than lab-reported data indicate, as per a new report.

Widening Gap In Lab and Real-World CO2 Output

Data reveals that PHEVs emit just 19% lower CO₂ than conventional gas and diesel cars, based on research conducted by a advocacy organization. That contrasts sharply with laboratory estimates, which suggested a 75% reduction in emissions.

Analysts studied data from onboard energy use meters of 800,000 cars sold in Europe from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while official figures are falling,” said a lead analyst participating in the report. “That gap is widening and creates a serious problem. Consequently, PHEVs emit almost as heavily as gasoline cars.”

Primary Factors Driving the Emissions Gap

Researchers attributed the majority of the difference to inflated estimates of the “utility factor” – the percentage of miles travelled in battery power compared to overall mileage. The team found that just a quarter of driving was completed in electric mode, whereas official assumptions suggested 84%.

Even, when operating in EV mode, pollution amounts were significantly higher than official projections. This happened because EV motors were not strong sufficient to operate alone, leading to engines using fossil fuels for almost a third of the distance covered in EV mode.

Policy and Financial Implications

Based on estimates, the underestimation of PHEV CO2 output enabled several large carmaker groups to avoid over €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs could pay about €500 more per year in operating expenses than is estimated under laboratory conditions.

“The bold statements that automakers often promote about their PHEV vehicles are clearly far from the mark,” commented a automotive expert. “Consumers are being duped into believing that by buying a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are little better than standard gas and diesel cars in terms of fuel use, CO₂ emissions, and operating costs.”

Policy Debate and Industry Lobbying

Plug-in hybrid cars have recently been drawn again into policy discussions as carmakers have pressed the EU to relax CO₂ targets. A proposed ban on sales of new combustion engine cars in 2035 has faced intense lobbying from the car industry and resistance from EU countries with significant automotive industries.

Some high-level politicians have suggested PHEVs as a possible “compromise” option to include in the regulation.

An external energy economics expert, who was unaffiliated with the research, called the report a “highly valuable addition” after years in which segments of the automotive sector claimed there was insufficient information to accurately evaluate actual CO2 output.

“The results show, beyond any doubt, that the gap between official and real-world PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or conventional cars,” they stated. “All policy changes concerning PHEVs should be made with extreme care and considering that evidence.”