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Plug-in hybrid electric vehicles release nearly five times greater global warming emissions than official data show, according to a recent report.

Widening Discrepancy Between Lab and Actual CO2 Output

Statistics reveals that PHEVs emit just 19% less CO₂ than conventional gas and diesel vehicles, according to analysis conducted by a advocacy group. That contrasts significantly with laboratory tests, which suggested a three-quarters reduction in pollution.

Analysts examined data from in-vehicle fuel consumption meters of 800,000 vehicles registered in the EU from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are decreasing,” said a lead analyst involved in the report. “This discrepancy is widening and creates a serious issue. Consequently, PHEVs pollute almost as heavily as petrol cars.”

Key Reasons Driving the Emissions Gap

Researchers linked the majority of the gap to overestimates of the “utility factor” – the percentage of kilometers travelled in electric mode relative to overall distance. The team found that just 27% of travel was completed in EV mode, while official assumptions assumed over four-fifths.

Even, when running in EV mode, emission amounts were well above lab estimates. That happened because electric motors were not strong enough to operate independently, resulting to combustion motors using gasoline for almost one-third of the distance covered in electric mode.

Regulatory and Economic Consequences

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

Furthermore, owners of PHEVs would pay about €500 extra annually in operating expenses than is assumed under lab tests.

“The bold statements that manufacturers often promote about their PHEV cars are clearly way off the mark,” stated a automotive expert. “Buyers are being misled into thinking that by buying a PHEV, they are helping the planet and cutting money. In reality, PHEVs are little improved than standard gas and diesel vehicles in terms of fuel use, CO₂ emissions, and operating expenses.”

Political Debate and Automotive Pressure

Hybrid cars have recently been brought back into political discussions as carmakers have lobbied the European Union to relax CO₂ targets. A planned prohibition on new internal combustion vehicles in 2035 has faced intense pressure from the car sector and opposition from member states with large automotive manufacturing.

Some high-level politicians have suggested PHEVs as a potential “compromise” solution to include in the regulation.

An external energy economics expert, who was not involved with the research, described the analysis a “very useful contribution” after a long period in which segments of the car industry argued there was too little information to accurately evaluate actual CO2 output.

“The results demonstrate, without question, that the difference between official and real-world PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or conventional cars,” they stated. “All policy adjustments regarding PHEVs should be made with utmost caution and in the light of this evidence.”