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PHEVs release almost five times greater planet-heating emissions than official data show, according to a new report.

Growing Discrepancy In Official and Real-World CO2 Output

Statistics reveals that PHEVs emit only one-fifth lower CO₂ than conventional petrol and diesel cars, based on research carried out by a non-profit group. This contrasts sharply with lab estimates, which assumed a three-quarters reduction in emissions.

Analysts examined data from in-vehicle fuel consumption monitors of eight hundred thousand vehicles registered in the EU from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are decreasing,” said a senior analyst involved in the report. “That discrepancy is widening and creates a significant issue. Consequently, PHEVs emit nearly as heavily as petrol vehicles.”

Key Reasons Driving the Discrepancy

Researchers attributed the majority of the gap to inflated estimates of the “utility factor” – the percentage of kilometers driven in battery mode compared to total mileage. The team found that just 27% of travel was completed in electric mode, whereas lab estimates suggested over four-fifths.

Additionally, when operating in EV mode, pollution amounts were significantly higher than lab estimates. That occurred because electric motors were insufficiently powerful sufficient to operate alone, resulting to engines burning gasoline for almost one-third of the distance completed in electric mode.

Policy and Economic Consequences

According to calculations, the lowballing of PHEV CO2 output allowed four large automaker companies to escape over €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ targets.

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

“The bold claims that automakers often promote about their plug-in hybrid vehicles are obviously far from the truth,” commented a automotive expert. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are little better than standard gas and diesel vehicles in terms of energy consumption, CO₂ production, and operating costs.”

Political Debate and Automotive Pressure

Hybrid vehicles have lately been drawn back into policy debates as carmakers have pressed the EU to relax CO₂ standards. A proposed ban on sales of new internal combustion cars in 2035 has faced intense pressure from the car industry and resistance from EU countries with significant automotive manufacturing.

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

One independent energy policy specialist, who was not involved with the research, described the analysis a “highly valuable contribution” after years in which segments of the automotive sector claimed there was too little data to accurately evaluate real-world emissions.

“The results demonstrate, beyond any doubt, that the gap between official and actual PHEV energy use and CO₂ emissions is significantly greater than for gasoline or diesel cars,” the expert stated. “All regulatory changes regarding PHEVs should be implemented with extreme caution and considering this data.”