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Plug-in hybrid electric vehicles release nearly 5x more global warming emissions than official figures show, according to a new report.

Widening Discrepancy In Official and Actual CO2 Output

Data reveals that PHEVs release only one-fifth lower CO₂ than conventional petrol and diesel cars, based on analysis conducted by a non-profit group. That contrasts sharply with laboratory tests, which assumed a 75% reduction in pollution.

Analysts studied data from in-vehicle fuel consumption meters of 800,000 cars registered in the EU from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab estimates, up from three and a half times in 2021.

“Actual CO2 output are increasing, while official figures are decreasing,” said a lead researcher participating in the study. “This gap is growing and poses a significant issue. As a result, PHEVs pollute nearly as heavily as gasoline vehicles.”

Primary Factors Driving the Discrepancy

Analysts linked the majority of the gap to overestimates of the “utility factor” – the percentage of miles driven in electric mode relative to total distance. The team found that just 27% of travel was done in EV mode, while official assumptions suggested 84%.

Even, when running in EV mode, emission levels were significantly higher than lab projections. This occurred because electric motors were insufficiently powerful enough to function alone, resulting to combustion motors burning gasoline for nearly a third of the distance completed in electric mode.

Policy and Financial Consequences

Based on calculations, the underestimation of PHEV CO2 output enabled four major carmaker groups to avoid more than €5bn in fines from 2021 and 2023, by falsely easing adherence with European Union fleet-average CO₂ targets.

Additionally, owners of PHEVs could spend approximately €500 more annually in operating expenses than is estimated under lab tests.

“The strong statements that manufacturers often promote about their plug-in hybrid cars are obviously far from the truth,” commented a transport analyst. “Buyers are being duped into believing that by buying a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are little improved than regular petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and running costs.”

Policy Discussion and Automotive Pressure

Hybrid vehicles have lately been brought again into political debates as carmakers have lobbied the EU to weaken CO₂ standards. A proposed ban on sales of new combustion engine cars in 2035 has faced heavy lobbying from the car sector and opposition from EU countries with significant automotive industries.

Several high-level officials have suggested plug-in hybrids as a potential “compromise” option to include in the legislation.

One independent energy economics expert, who was not involved with the research, called the report a “very useful addition” after years in which parts of the automotive sector claimed there was insufficient information to accurately evaluate actual CO2 output.

“The results demonstrate, beyond any doubt, that the difference in official and real-world PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or conventional cars,” the expert said. “All policy changes regarding PHEVs should be made with extreme caution and considering that data.”