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PHEVs emit nearly 5x greater planet-heating emissions than official data indicate, according to a recent report.

Widening Discrepancy In Lab and Actual CO2 Output

Statistics shows that PHEVs emit only 19% lower CO₂ than conventional gas and diesel cars, based on research conducted by a non-profit group. That contrasts significantly with laboratory estimates, which assumed a 75% reduction in pollution.

Researchers studied information from onboard energy use meters of 800,000 cars sold in the EU from 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, up from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported emissions are falling,” said a lead researcher involved in the report. “This gap is widening and creates a significant issue. Consequently, PHEVs pollute almost as heavily as petrol vehicles.”

Key Reasons Behind the Discrepancy

Researchers attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers driven in electric mode relative to overall mileage. The team found that only a quarter of travel was completed in electric mode, while official assumptions suggested 84%.

Additionally, when operating in electric mode, pollution levels were significantly higher than official estimates. That happened because electric motors were insufficiently powerful sufficient to function independently, resulting to engines using fossil fuels for nearly a third of the distance covered in electric mode.

Regulatory and Financial Consequences

According to estimates, the lowballing of PHEV emissions enabled four major carmaker groups to escape over €5bn in fines from 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 is assumed under lab conditions.

“The bold claims that automakers often promote about their plug-in hybrid cars are clearly way off the truth,” commented a transport expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are little better than regular gas and diesel vehicles in terms of fuel consumption, CO₂ production, and operating costs.”

Political Debate and Industry Pressure

Plug-in hybrid vehicles have recently been drawn again into policy debates as carmakers have lobbied the European Union to relax CO₂ standards. A planned ban on sales of new combustion engine cars in 2035 has faced heavy lobbying from the car industry and resistance from EU countries with large automotive manufacturing.

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

An independent energy policy specialist, who was unaffiliated with the research, described the report a “very useful contribution” after years in which parts of the car industry argued there was insufficient information to accurately evaluate real-world CO2 output.

“The results show, without question, that the difference in official and real-world PHEV fuel consumption and CO₂ output is much, much larger than for petrol or conventional cars,” the expert stated. “Any policy changes concerning PHEVs should be implemented with utmost caution and in the light of that data.”