🔗 Share this article

Plug-in hybrid cars produce almost 5x greater planet-heating emissions than official data show, according to a recent analysis.

Widening Gap Between Lab and Real-World Emissions

Statistics reveals that PHEVs release only 19% less CO₂ than traditional petrol and diesel cars, according to analysis carried out by a advocacy organization. That differs significantly with lab estimates, which suggested a three-quarters decrease in pollution.

Analysts examined data from in-vehicle energy use monitors of eight hundred thousand cars registered in Europe between 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, increased from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are falling,” said a lead analyst participating in the report. “This gap is growing and poses a significant issue. As a result, PHEVs pollute almost as heavily as petrol cars.”

Key Factors Behind the Discrepancy

Researchers attributed most of the gap to overestimates of the “utility factor” – the percentage of miles travelled in battery mode relative to total mileage. The team found that just a quarter of travel was done in electric mode, while lab assumptions assumed over four-fifths.

Even, when operating in electric mode, emission amounts were well above lab estimates. This happened because electric motors were insufficiently powerful sufficient to function independently, leading to combustion motors using gasoline for nearly one-third of the travel covered in electric mode.

Policy and Economic Implications

Based on estimates, the lowballing of PHEV CO2 output enabled four large automaker groups to escape over €5bn in penalties between 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ targets.

Furthermore, owners of PHEVs could pay about €500 more annually in operating costs than is assumed under laboratory tests.

“The strong claims that automakers like to make about their PHEV vehicles are clearly way off the mark,” commented a automotive expert. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are only slightly better than regular petrol and diesel vehicles in terms of fuel use, CO₂ production, and running costs.”

Policy Debate and Automotive Pressure

Hybrid vehicles have recently been brought again into policy discussions as automakers have pressed the EU to weaken CO₂ standards. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the car sector and opposition from EU countries with large automotive manufacturing.

Several high-level officials have proposed PHEVs as a possible “compromise” solution to include in the regulation.

One external energy policy expert, who was unaffiliated with the research, described the analysis a “very useful addition” after years in which segments of the automotive sector claimed there was too little information to properly assess real-world CO2 output.

“These findings show, without question, that the difference between official and actual PHEV energy use and CO₂ emissions is much, much larger than for petrol or conventional vehicles,” the expert stated. “All policy changes regarding PHEVs should be made with extreme caution and considering that evidence.”