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Plug-in hybrid cars emit almost 5x more global warming emissions than official figures indicate, as per a new analysis.

Widening Discrepancy In Official and Actual Emissions

Data reveals that PHEVs release only one-fifth less CO₂ than conventional gas and diesel cars, based on research carried out by a advocacy group. That contrasts sharply with laboratory estimates, which assumed a 75% decrease in emissions.

Analysts studied information from in-vehicle fuel consumption monitors of 800,000 cars sold in Europe between 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official figures, increased from three and a half times in 2021.

“Actual CO2 output are rising, while official figures are decreasing,” stated a lead analyst participating in the report. “That discrepancy is growing and creates a serious issue. As a result, PHEVs pollute nearly as heavily as gasoline vehicles.”

Key Factors Driving the Emissions Gap

Analysts linked most of the difference to inflated estimates of the “utility factor” – the ratio of miles driven in electric mode relative to overall distance. They determined that only a quarter of travel was completed in EV mode, whereas lab assumptions suggested 84%.

Even, when operating in EV mode, pollution amounts were well above official projections. This happened because electric motors were insufficiently powerful enough to operate alone, resulting to engines burning gasoline for almost a third of the travel completed in EV mode.

Policy and Economic Implications

According to calculations, the underestimation of PHEV emissions allowed several major automaker groups to avoid more than €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ targets.

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

“The strong claims that manufacturers often promote about their plug-in hybrid vehicles are clearly way off the truth,” commented a transport analyst. “Buyers are being duped into believing that by buying a PHEV, they are helping the planet and saving costs. In reality, PHEVs are little improved than regular petrol and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running expenses.”

Policy Debate and Automotive Lobbying

Plug-in hybrid vehicles have recently been brought back into policy debates as carmakers have pressed the EU to weaken CO₂ standards. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced intense pressure from the car sector and opposition from EU countries with large automotive industries.

Some senior politicians have proposed plug-in hybrids as a possible “compromise” solution to introduce in the legislation.

An external energy policy specialist, who was not involved with the study, called the analysis a “very useful contribution” after a long period in which parts of the car sector argued there was insufficient information to properly assess real-world emissions.

“These findings demonstrate, beyond any doubt, that the difference between lab and real-world PHEV energy use and CO₂ emissions is significantly larger than for gasoline or diesel cars,” they said. “All policy changes concerning PHEVs should be implemented with extreme caution and in the light of that data.”