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Plug-in hybrid electric vehicles release almost five times more planet-heating emissions than lab-reported figures show, according to a recent report.

Growing Discrepancy Between Official and Real-World CO2 Output

Data shows that PHEVs emit only one-fifth lower CO₂ than conventional petrol and diesel cars, according to analysis conducted by a advocacy organization. This contrasts sharply with laboratory estimates, which assumed a three-quarters reduction in pollution.

Researchers examined information from in-vehicle fuel consumption monitors of 800,000 cars registered in Europe from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than lab estimates, up from 3.5 times in 2021.

“Actual CO2 output are rising, while official figures are decreasing,” stated a lead analyst involved in the report. “That discrepancy is growing and creates a serious problem. Consequently, PHEVs emit nearly as much as gasoline cars.”

Primary Reasons Driving the Emissions Gap

Analysts linked the majority of the gap to inflated estimates of the “electric driving share” – the percentage of miles travelled in battery mode relative to overall distance. They determined that only 27% of driving was completed in electric mode, while lab assumptions assumed 84%.

Even, when operating in electric mode, emission amounts were well above lab estimates. This occurred because electric motors were not strong enough to operate alone, leading to combustion motors using fossil fuels for almost a third of the distance covered in electric mode.

Policy and Financial Consequences

According to estimates, the lowballing of PHEV CO2 output enabled four major automaker groups to escape more than €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs could spend about €500 extra annually in operating expenses than would be estimated under lab conditions.

“The bold claims that manufacturers often promote about their PHEV vehicles are clearly way off the truth,” commented a transport analyst. “Consumers are being duped into thinking that by buying a PHEV, they are helping the planet and saving costs. Actually, PHEVs are little improved than regular gas and diesel vehicles in terms of fuel use, CO₂ emissions, and running costs.”

Political Debate and Industry Pressure

Hybrid vehicles have recently been brought back into political discussions as automakers have pressed the EU to relax CO₂ standards. A proposed ban on new internal combustion cars in 2035 has faced intense lobbying from the car industry and resistance from member states with significant car industries.

Several senior officials have suggested PHEVs as a possible “compromise” solution to introduce in the regulation.

One independent energy policy expert, who was not involved with the study, called the report a “highly valuable addition” after a long period in which parts of the automotive sector claimed there was too little data to accurately evaluate actual emissions.

“The results show, beyond any doubt, that the gap between official and actual PHEV energy use and CO₂ output is much, much larger than for gasoline or diesel cars,” they stated. “Any policy changes regarding PHEVs should be implemented with utmost caution and considering that evidence.”