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Plug-in hybrid cars produce almost 5x greater global warming pollution than official data indicate, according to a recent analysis.

Widening Gap Between Official and Actual CO2 Output

Data shows that PHEVs emit just one-fifth less CO₂ than traditional petrol and diesel cars, based on research carried out by a non-profit organization. That differs sharply with lab tests, which assumed a 75% decrease in pollution.

Analysts examined data from in-vehicle fuel consumption meters of eight hundred thousand vehicles sold in Europe between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab figures, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are decreasing,” stated a senior researcher involved in the report. “That gap is growing and creates a serious problem. Consequently, PHEVs emit nearly as much as petrol cars.”

Primary Reasons Driving the Emissions Gap

Analysts linked most of the gap to overestimates of the “utility factor” – the ratio of kilometers travelled in electric power relative to overall distance. They determined that just a quarter of travel was completed in electric mode, while lab estimates suggested over four-fifths.

Additionally, when running in electric mode, emission amounts were significantly higher than lab estimates. That happened because EV motors were not strong enough to operate independently, leading to combustion motors using fossil fuels for nearly a third of the travel covered in electric mode.

Regulatory and Economic Consequences

Based on calculations, the underestimation of PHEV emissions enabled four major carmaker companies to avoid more than €5bn in fines from 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs could pay approximately €500 more per year in running expenses than is estimated under lab conditions.

“The strong statements that automakers like to make about their plug-in hybrid vehicles 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 cutting costs. In reality, PHEVs are only slightly improved than standard petrol and diesel cars in terms of energy use, CO₂ production, and running expenses.”

Policy Discussion and Industry Pressure

Hybrid vehicles have lately been brought back into political debates as carmakers have pressed the EU to weaken CO₂ targets. A proposed prohibition on sales of new combustion engine cars in 2035 has faced heavy pressure from the automotive industry and resistance from EU countries with large car manufacturing.

Some senior officials have proposed plug-in hybrids as a possible “compromise” option to include in the regulation.

An independent energy economics specialist, who was unaffiliated with the research, described the report a “highly valuable addition” after years in which parts of the car sector claimed there was insufficient data to properly assess real-world emissions.

“The results demonstrate, beyond any doubt, that the gap in lab and actual PHEV energy use and CO₂ emissions is significantly greater than for petrol or conventional vehicles,” they stated. “All regulatory changes concerning PHEVs should be implemented with extreme care and in the light of that data.”