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Plug-in hybrid cars release almost 5x greater global warming pollution than official data show, as per a recent report.

Widening Gap In Lab and Real-World CO2 Output

Statistics shows that PHEVs emit only 19% lower CO₂ than conventional petrol and diesel cars, according to analysis carried out by a advocacy group. This differs sharply with laboratory tests, which suggested a three-quarters reduction in pollution.

Analysts studied information from onboard fuel consumption monitors of eight hundred thousand cars sold in Europe 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.

“Real-world emissions are increasing, while official figures are falling,” said a lead analyst participating in the study. “That gap is widening and creates a significant problem. As a result, PHEVs emit almost as much as gasoline cars.”

Primary Factors Driving the Emissions Gap

Analysts linked most of the gap to overestimates of the “electric driving share” – the percentage of miles travelled in battery power compared to overall distance. The team found that just 27% of driving was completed in electric mode, whereas lab assumptions assumed 84%.

Additionally, when operating in electric mode, pollution amounts were well above lab estimates. This happened because electric motors were not strong enough to function alone, leading to engines using fossil fuels for nearly a third of the distance covered in electric mode.

Policy and Financial Consequences

Based on estimates, the underestimation of PHEV CO2 output enabled four large automaker companies to avoid more than €5bn in penalties between 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ targets.

Additionally, owners of PHEVs would spend about €500 extra per year in operating expenses than is assumed under laboratory tests.

“The strong statements that manufacturers like to make about their plug-in hybrid cars are clearly far from the truth,” commented a automotive analyst. “Buyers are being duped into believing that by buying a PHEV, they are helping the environment and saving costs. Actually, PHEVs are only slightly better than standard gas and diesel cars in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Political Debate and Industry Pressure

Hybrid vehicles have lately been drawn again into policy discussions as automakers have pressed the EU to weaken CO₂ standards. A proposed prohibition on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the automotive industry and resistance from EU countries with significant car industries.

Some high-level officials have suggested plug-in hybrids as a potential “flexibility” option to introduce in the regulation.

One external energy policy specialist, who was unaffiliated with the research, called the analysis a “very useful addition” after years in which segments of the car industry argued there was insufficient information to properly evaluate actual CO2 output.

“These findings demonstrate, beyond any doubt, that the difference in lab and actual PHEV energy use and CO₂ output is significantly larger than for gasoline or conventional cars,” the expert stated. “Any policy changes regarding PHEVs should be implemented with utmost caution and in the light of this data.”