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Plug-in hybrid cars produce nearly 5x more planet-heating emissions than lab-reported data indicate, according to a new analysis.

Growing Gap Between Lab and Actual Emissions

Statistics shows that PHEVs release only 19% less CO₂ than conventional petrol and diesel vehicles, according to analysis conducted by a non-profit group. This contrasts significantly with laboratory tests, which assumed a 75% decrease in emissions.

Researchers examined data from onboard fuel consumption monitors of eight hundred thousand cars sold in the EU between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than official estimates, increased from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported figures are falling,” stated a senior researcher involved in the study. “This discrepancy is growing and creates a serious issue. As a result, PHEVs pollute nearly as much as petrol vehicles.”

Key Reasons Driving the Discrepancy

Analysts attributed most of the gap to overestimates of the “utility factor” – the percentage of kilometers travelled in battery power compared to total distance. The team determined that just 27% of travel was completed in EV mode, while official assumptions suggested 84%.

Even, when running in EV mode, emission amounts were well above official estimates. This happened because EV motors were insufficiently powerful enough to operate independently, leading to combustion motors using fossil fuels for nearly a third of the distance completed in electric mode.

Policy and Financial Consequences

According to estimates, the underestimation of PHEV emissions enabled several major carmaker companies to avoid over €5bn in fines from 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs would pay approximately €500 extra per year in running expenses than is estimated under laboratory conditions.

“The bold claims that automakers often promote about their PHEV cars are clearly far from the truth,” commented 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 better than regular gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running costs.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid vehicles have lately been brought again into political debates as carmakers have pressed the European Union to relax CO₂ standards. A planned ban on sales of new combustion engine cars in 2035 has faced intense pressure from the automotive sector and opposition from member states with significant automotive industries.

Some senior officials have proposed plug-in hybrids as a potential “flexibility” option to introduce in the regulation.

An external energy economics expert, who was unaffiliated with the research, called the report a “very useful contribution” after a long period in which segments of the car industry claimed there was insufficient information to properly assess actual emissions.

“The results show, without question, that the difference between lab and real-world PHEV fuel consumption and CO₂ output is significantly greater than for petrol or diesel cars,” the expert said. “All regulatory adjustments regarding PHEVs should be implemented with utmost care and considering that data.”