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Plug-in hybrid electric vehicles release almost five times greater planet-heating emissions than lab-reported figures indicate, as per a new report.

Widening Gap Between Lab and Actual CO2 Output

Data shows that PHEVs emit just one-fifth lower CO₂ than traditional gas and diesel cars, according to analysis conducted by a non-profit group. This differs significantly with laboratory estimates, which assumed a three-quarters reduction in emissions.

Analysts studied information from in-vehicle energy use meters of 800,000 cars sold in the EU from 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are decreasing,” stated a senior researcher participating in the report. “This gap is growing and creates a serious problem. As a result, PHEVs pollute almost as heavily as petrol vehicles.”

Primary Factors Behind the Discrepancy

Analysts linked the majority of the gap to overestimates of the “utility factor” – the ratio of kilometers driven in electric power compared to overall distance. The team found that only 27% of driving was completed in EV mode, whereas official estimates suggested 84%.

Even, when operating in EV mode, pollution amounts were significantly higher than official estimates. This occurred because electric motors were insufficiently powerful enough to operate alone, resulting to combustion motors burning fossil fuels for almost a third of the travel covered in electric mode.

Regulatory and Financial Consequences

According to calculations, the underestimation of PHEV emissions allowed several large carmaker groups to avoid over €5bn in fines from 2021 and 2023, by artificially easing adherence with EU average fleet CO₂ standards.

Furthermore, drivers of PHEVs could pay approximately €500 more per year in operating expenses than is assumed under laboratory conditions.

“The bold claims that manufacturers often promote about their PHEV cars are clearly way off the mark,” commented a automotive analyst. “Buyers are being misled into believing that by buying a PHEV, they are helping the planet and saving costs. In reality, PHEVs are only slightly better than standard petrol and diesel cars in terms of fuel consumption, CO₂ production, and running expenses.”

Policy Discussion and Industry Pressure

Hybrid vehicles have recently been drawn again into policy discussions as carmakers have pressed the EU to weaken CO₂ targets. A planned ban on new combustion engine vehicles in 2035 has faced heavy pressure from the automotive sector and resistance from member states with significant automotive manufacturing.

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

One independent energy policy expert, who was not involved with the research, called the analysis a “highly valuable addition” after years in which parts of the automotive industry claimed there was insufficient data to accurately evaluate real-world CO2 output.

“The results demonstrate, without question, that the gap between lab and actual PHEV energy use and CO₂ emissions is much, much greater than for petrol or diesel vehicles,” the expert stated. “All policy adjustments concerning PHEVs should be implemented with utmost care and considering that data.”