🔗 Share this article

Plug-in hybrid cars produce nearly five times greater planet-heating pollution than lab-reported figures show, according to a recent report.

Widening Discrepancy In Lab and Real-World CO2 Output

Statistics shows that PHEVs release only one-fifth lower CO₂ than traditional petrol and diesel vehicles, based on analysis carried out by a non-profit organization. That differs significantly with laboratory estimates, which suggested a three-quarters reduction in pollution.

Researchers examined information from in-vehicle fuel consumption monitors of eight hundred thousand cars sold in the EU between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab figures, 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. “That gap is widening and creates a significant issue. Consequently, PHEVs emit nearly as heavily as petrol vehicles.”

Key Factors Driving the Discrepancy

Analysts attributed most of the gap to inflated estimates of the “utility factor” – the ratio of kilometers travelled in electric mode compared to total distance. They found that just a quarter of driving was completed in electric mode, whereas official estimates suggested over four-fifths.

Additionally, when running in EV mode, emission levels were significantly higher than lab projections. This occurred because EV motors were not strong enough to operate alone, resulting to combustion motors using gasoline for nearly one-third of the travel completed in EV mode.

Regulatory and Financial Consequences

According to estimates, the underestimation of PHEV emissions enabled several large carmaker groups to avoid over €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ targets.

Additionally, owners of PHEVs would spend about €500 extra annually in running costs than would be estimated under laboratory tests.

“The strong statements that automakers often promote about their plug-in hybrid cars are clearly far from the truth,” stated a transport analyst. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are little improved than regular petrol and diesel cars in terms of energy use, CO₂ production, and operating expenses.”

Political Debate and Automotive Pressure

Plug-in hybrid cars have recently been drawn again into policy discussions as carmakers have lobbied the European Union to weaken CO₂ standards. A proposed prohibition on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the automotive sector and resistance from member states with large automotive manufacturing.

Several senior officials have proposed PHEVs as a possible “compromise” option to introduce in the legislation.

One external energy economics expert, who was not involved with the research, described the analysis a “very useful contribution” after years in which segments of the automotive industry claimed there was insufficient information to properly assess actual emissions.

“These findings demonstrate, without question, that the gap in lab and real-world PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or conventional vehicles,” the expert stated. “Any policy changes concerning PHEVs should be made with utmost caution and considering this data.”