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Plug-in hybrid cars emit almost 5x greater global warming emissions than lab-reported figures show, according to a recent report.

Growing Discrepancy Between Lab and Real-World Emissions

Statistics reveals that PHEVs emit only 19% lower CO₂ than traditional gas and diesel vehicles, based on research carried out by a advocacy group. That differs significantly with lab tests, which assumed a three-quarters reduction in pollution.

Analysts studied data from onboard fuel consumption monitors of eight hundred thousand vehicles sold in Europe from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, up from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported figures are decreasing,” said a senior researcher participating in the report. “This discrepancy is widening and poses a significant issue. Consequently, PHEVs emit nearly as heavily as petrol cars.”

Key Factors Driving the Emissions Gap

Analysts linked most of the gap to inflated estimates of the “utility factor” – the ratio of miles driven in electric mode relative to overall distance. They determined that only a quarter of travel was done in electric mode, whereas lab assumptions suggested 84%.

Additionally, when running in electric mode, emission amounts were significantly higher than lab estimates. This happened because electric motors were insufficiently powerful enough to function alone, leading to combustion motors using gasoline for nearly one-third of the distance covered in electric mode.

Policy and Economic Consequences

Based on calculations, the underestimation of PHEV CO2 output allowed four large carmaker groups to avoid over €5bn in fines from 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ targets.

Furthermore, drivers of PHEVs would pay about €500 more annually in operating expenses than is estimated under lab conditions.

“The strong statements that manufacturers often promote about their PHEV vehicles are obviously far from the mark,” commented a automotive analyst. “Buyers are being misled into thinking that by buying a PHEV, they are helping the environment and saving money. In reality, PHEVs are little improved than regular gas and diesel cars in terms of fuel consumption, CO₂ emissions, and operating costs.”

Policy Debate and Automotive Pressure

Hybrid cars have lately been drawn back into policy discussions as automakers have pressed the EU to weaken CO₂ targets. A planned ban on new combustion engine cars in 2035 has faced heavy lobbying from the car industry and resistance from EU countries with significant automotive manufacturing.

Some senior officials have suggested plug-in hybrids as a potential “flexibility” option to include in the legislation.

One external energy economics specialist, who was not involved with the research, called the report a “very useful contribution” after a long period in which parts of the car industry argued there was too little information to accurately assess real-world CO2 output.

“The results demonstrate, without question, that the gap between official and real-world PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or diesel vehicles,” they stated. “Any policy changes concerning PHEVs should be made with utmost caution and considering this evidence.”