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Plug-in hybrid cars release nearly five times greater planet-heating pollution than lab-reported data show, according to a new report.

Widening Gap Between Lab and Actual CO2 Output

Statistics reveals that PHEVs emit just one-fifth less CO₂ than conventional gas and diesel cars, based on analysis conducted by a advocacy organization. That contrasts significantly with laboratory estimates, which assumed a 75% decrease in pollution.

Researchers studied data from onboard fuel consumption monitors of 800,000 vehicles sold in the EU from 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, increased from three and a half times in 2021.

“Actual emissions are rising, while official emissions are falling,” said a lead researcher involved in the study. “That discrepancy is widening and poses a serious problem. Consequently, PHEVs pollute nearly as heavily as gasoline vehicles.”

Key Factors Driving the Emissions Gap

Analysts attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in electric mode relative to overall distance. The team determined that just a quarter of driving was completed in electric mode, whereas official estimates assumed 84%.

Even, when running in EV mode, pollution amounts were well above official projections. This happened because EV motors were insufficiently powerful sufficient to operate alone, resulting to engines burning fossil fuels for almost a third of the distance completed in electric mode.

Policy and Economic Consequences

Based on estimates, the lowballing of PHEV emissions allowed four large automaker groups to escape over €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs could pay approximately €500 more annually in operating expenses than is assumed under lab tests.

“The strong statements that automakers often promote about their PHEV cars are obviously far from the truth,” stated a automotive expert. “Consumers are being duped into believing that by buying a PHEV, they are helping the environment and cutting money. In reality, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running costs.”

Policy Debate and Industry Lobbying

Plug-in hybrid cars have recently been drawn again into policy debates as carmakers have pressed the European Union to weaken CO₂ standards. A proposed ban on sales of new internal combustion cars in 2035 has faced intense lobbying from the car industry and opposition from member states with large automotive industries.

Some high-level officials have proposed plug-in hybrids as a possible “compromise” option to include in the regulation.

One external energy policy specialist, who was not involved with the research, described the report a “highly valuable contribution” after years in which parts of the car industry claimed there was insufficient information to properly evaluate actual emissions.

“The results show, without question, that the difference in lab and actual PHEV fuel consumption and CO₂ output is significantly greater than for petrol or conventional vehicles,” they stated. “Any regulatory adjustments concerning PHEVs should be implemented with utmost care and considering this data.”