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Plug-in hybrid cars emit almost 5x greater global warming emissions than official data indicate, according to a recent analysis.

Growing Discrepancy Between Lab and Actual CO2 Output

Data reveals that PHEVs release just one-fifth lower CO₂ than conventional petrol and diesel vehicles, according to analysis carried out by a advocacy organization. This contrasts significantly with lab tests, which assumed a three-quarters decrease in emissions.

Analysts studied data from in-vehicle fuel consumption monitors of eight hundred thousand cars sold in Europe between 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official figures, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are decreasing,” stated a senior researcher participating in the study. “That discrepancy is growing and creates a significant issue. Consequently, PHEVs emit almost as heavily as petrol cars.”

Key Factors Driving the Discrepancy

Researchers attributed the majority of the gap to overestimates of the “utility factor” – the ratio of kilometers travelled in battery mode compared to total mileage. They found that only a quarter of driving was done in electric mode, whereas official assumptions suggested over four-fifths.

Even, when operating in EV mode, pollution levels were well above lab projections. This occurred because electric motors were insufficiently powerful sufficient to operate independently, resulting to combustion motors using fossil fuels for nearly one-third of the travel completed in electric mode.

Policy and Financial Implications

According to estimates, the lowballing of PHEV emissions enabled several large automaker groups to avoid over €5bn in fines between 2021 and 2023, by falsely easing adherence with EU fleet-average CO₂ targets.

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

“The strong statements that manufacturers often promote about their plug-in hybrid cars are obviously way off the mark,” stated a automotive expert. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of fuel use, CO₂ emissions, and operating costs.”

Policy Debate and Automotive Pressure

Hybrid cars have lately been brought again into political debates as carmakers have pressed the European Union to relax CO₂ standards. A planned prohibition on new internal combustion vehicles in 2035 has faced heavy pressure from the automotive sector and resistance from member states with significant car industries.

Several senior politicians have proposed PHEVs as a potential “compromise” solution to introduce in the legislation.

An independent energy policy expert, who was not involved with the study, called the report a “very useful contribution” after years in which segments of the automotive sector claimed there was too little data to properly evaluate actual emissions.

“These findings show, without question, that the difference in official and real-world PHEV energy use and CO₂ output is much, much greater than for gasoline or conventional vehicles,” they said. “Any regulatory adjustments regarding PHEVs should be made with utmost caution and in the light of that data.”