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Plug-in hybrid cars produce nearly 5x greater global warming emissions than lab-reported figures indicate, according to a new analysis.

Growing Gap In Official and Real-World Emissions

Statistics shows that PHEVs release just 19% less CO₂ than conventional petrol and diesel vehicles, based on research conducted by a advocacy organization. This contrasts significantly with lab estimates, which assumed a 75% reduction in emissions.

Analysts examined information from in-vehicle energy use monitors of 800,000 cars sold in the EU from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, up from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are falling,” stated a senior analyst participating in the study. “That discrepancy is growing and creates a significant issue. As a result, PHEVs pollute nearly as much as gasoline cars.”

Key Reasons Driving the Discrepancy

Analysts attributed most of the gap to overestimates of the “utility factor” – the ratio of miles travelled in battery mode compared to total mileage. They determined that only 27% of travel was completed in EV mode, whereas lab estimates assumed over four-fifths.

Even, when running in EV mode, pollution amounts were significantly higher than lab projections. This occurred because electric motors were not strong enough to function independently, resulting to engines using fossil fuels for almost one-third of the distance covered in EV mode.

Policy and Economic Consequences

Based on calculations, the underestimation of PHEV CO2 output enabled four large automaker companies to avoid over €5bn in fines between 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ standards.

Furthermore, owners of PHEVs would spend approximately €500 more annually in running expenses than would be estimated under laboratory conditions.

“The strong claims that manufacturers like to make about their PHEV vehicles are clearly way off the truth,” commented a transport analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of energy consumption, CO₂ production, and running costs.”

Political Discussion and Industry Pressure

Hybrid cars have lately been brought again into policy debates as carmakers have lobbied the EU to relax CO₂ standards. A planned prohibition on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the car industry and opposition from EU countries with large automotive industries.

Several high-level officials have proposed PHEVs as a possible “compromise” solution to introduce in the legislation.

One external energy policy expert, who was unaffiliated with the research, called the report a “highly valuable addition” after a long period in which parts of the automotive sector argued there was too little data to properly evaluate actual emissions.

“The results show, without question, that the gap between lab and real-world PHEV fuel consumption and CO₂ output is significantly greater than for petrol or conventional cars,” they stated. “All policy changes concerning PHEVs should be made with utmost caution and considering that evidence.”