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Plug-in hybrid cars release almost 5x more planet-heating emissions than official figures indicate, as per a new analysis.

Growing Gap In Official and Real-World CO2 Output

Data reveals that PHEVs emit just 19% less CO₂ than conventional petrol and diesel cars, according to analysis carried out by a non-profit group. That differs significantly with laboratory tests, which assumed a three-quarters reduction in emissions.

Analysts studied data from in-vehicle fuel consumption monitors of 800,000 cars sold in Europe between 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, increased from three and a half times in 2021.

“Actual CO2 output are increasing, while official figures are decreasing,” said a lead analyst involved in the report. “This discrepancy is growing and creates a significant problem. Consequently, PHEVs pollute almost as heavily as petrol cars.”

Primary Factors Behind the Discrepancy

Analysts linked the majority of the gap to overestimates of the “utility factor” – the ratio of kilometers driven in battery mode relative to overall distance. The team determined that just 27% of driving was completed in EV mode, whereas lab assumptions assumed over four-fifths.

Even, when operating in EV mode, emission amounts were well above official projections. That occurred because EV motors were insufficiently powerful enough to operate independently, leading to engines burning fossil fuels for almost one-third of the travel covered in electric mode.

Policy and Financial Implications

Based on estimates, the lowballing of PHEV emissions enabled four large carmaker groups to avoid more than €5bn in penalties between 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ standards.

Additionally, owners of PHEVs would spend approximately €500 more per year in operating costs than is estimated under lab conditions.

“The strong statements that automakers like to make about their plug-in hybrid cars are clearly way off the truth,” stated a automotive expert. “Buyers are being misled into believing that by buying a PHEV, they are helping the planet and saving costs. Actually, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and running expenses.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid vehicles have recently been drawn back into policy debates as automakers have pressed the EU to weaken CO₂ standards. A planned ban on sales of new combustion engine cars in 2035 has faced heavy pressure from the car industry and resistance from EU countries with large car manufacturing.

Some high-level officials have suggested plug-in hybrids as a possible “compromise” solution to include in the legislation.

One external energy policy specialist, who was not involved with the research, described the analysis a “very useful contribution” after a long period in which segments of the automotive industry argued there was too little data to properly assess real-world emissions.

“The results show, without question, that the gap between official and actual PHEV fuel consumption and CO₂ output is much, much greater than for petrol or conventional vehicles,” the expert said. “Any regulatory adjustments regarding PHEVs should be made with utmost care and in the light of that data.”