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Plug-in hybrid cars emit nearly 5x more planet-heating pollution than lab-reported figures show, according to a recent analysis.

Growing Discrepancy In Lab and Real-World Emissions

Data shows that PHEVs release just 19% lower CO₂ than traditional gas and diesel vehicles, according to analysis carried out by a non-profit organization. This differs sharply with lab estimates, which assumed a three-quarters reduction in emissions.

Researchers studied data from in-vehicle energy use meters of eight hundred thousand cars registered in Europe from 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, up from three and a half times in 2021.

“Actual CO2 output are increasing, while official emissions are falling,” stated a lead researcher involved in the study. “This discrepancy is growing and creates a serious problem. As a result, PHEVs pollute almost as heavily as petrol cars.”

Key Reasons Behind the Discrepancy

Researchers attributed most of the gap to inflated estimates of the “utility factor” – the percentage of kilometers driven in battery mode relative to total distance. They determined that just 27% of driving was completed in electric mode, while lab estimates suggested over four-fifths.

Even, when running in EV mode, emission amounts were well above lab estimates. This happened because electric motors were insufficiently powerful enough to operate alone, resulting to engines burning fossil fuels for almost a third of the distance covered in electric mode.

Regulatory and Financial Consequences

According to calculations, the underestimation of PHEV emissions enabled four large carmaker companies to avoid over €5bn in penalties from 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ standards.

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

“The bold statements that automakers often promote about their plug-in hybrid cars are obviously way off the truth,” stated a transport expert. “Buyers are being duped into believing that by buying a PHEV, they are benefiting the environment and cutting costs. In reality, PHEVs are little improved than standard gas and diesel vehicles in terms of energy consumption, CO₂ emissions, and running costs.”

Political Discussion and Industry Lobbying

Hybrid vehicles have lately been drawn back into policy discussions as automakers have lobbied the EU to weaken CO₂ targets. A proposed ban on sales of new internal combustion vehicles in 2035 has faced intense lobbying from the car industry and opposition from member states with large car manufacturing.

Some high-level politicians have proposed PHEVs as a potential “compromise” solution to introduce in the regulation.

One external energy policy expert, who was unaffiliated with the study, called the report a “highly valuable contribution” after a long period in which parts of the car industry claimed there was insufficient data to properly assess real-world emissions.

“The results demonstrate, without question, that the difference in lab and real-world PHEV energy use and CO₂ output is much, much greater than for petrol or conventional vehicles,” the expert said. “All regulatory adjustments regarding PHEVs should be made with utmost care and considering this data.”