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PHEVs produce nearly 5x more planet-heating emissions than lab-reported figures show, according to a new analysis.

Growing Discrepancy Between Lab and Actual CO2 Output

Statistics shows that PHEVs emit just 19% less CO₂ than traditional petrol and diesel vehicles, according to analysis conducted by a advocacy group. This differs significantly with lab tests, which suggested a three-quarters decrease in pollution.

Researchers studied data from onboard fuel consumption meters of 800,000 vehicles registered in the EU from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab figures, up from three and a half times in 2021.

“Real-world emissions are rising, while official figures are falling,” said a senior researcher participating in the study. “This discrepancy is widening and poses a serious problem. As a result, PHEVs emit almost as much as petrol cars.”

Primary Factors Behind the Discrepancy

Analysts attributed most of the gap to overestimates of the “utility factor” – the ratio of kilometers travelled in electric mode relative to overall mileage. They found that only a quarter of driving was done in EV mode, while official assumptions suggested 84%.

Even, when running in EV mode, emission levels were significantly higher than lab estimates. That happened because electric motors were insufficiently powerful sufficient to function independently, resulting to combustion motors burning fossil fuels for nearly one-third of the distance covered in EV mode.

Policy and Financial Consequences

According to estimates, the lowballing of PHEV CO2 output allowed several major carmaker groups to escape more than €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs would pay about €500 extra annually in operating costs than is estimated under lab tests.

“The strong statements that manufacturers often promote about their plug-in hybrid cars are obviously way off the truth,” commented a transport expert. “Buyers are being duped into believing that by buying a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are only slightly better than standard gas and diesel cars in terms of fuel consumption, CO₂ emissions, and operating costs.”

Political Discussion and Automotive Lobbying

Hybrid vehicles have lately been brought back into policy debates as carmakers have pressed the EU to relax CO₂ targets. A planned ban on new internal combustion vehicles in 2035 has faced intense pressure from the car sector and opposition from EU countries with significant car industries.

Some high-level politicians have suggested plug-in hybrids as a potential “flexibility” option to include in the legislation.

An external energy economics specialist, who was unaffiliated with the study, described the analysis a “highly valuable addition” after years in which parts of the car industry claimed there was too little data to properly assess actual CO2 output.

“The results demonstrate, without question, that the gap between official and actual PHEV fuel consumption and CO₂ output is much, much greater than for petrol or diesel vehicles,” they stated. “Any regulatory adjustments regarding PHEVs should be made with utmost care and considering that data.”