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Plug-in hybrid electric vehicles release almost 5x more planet-heating pollution than lab-reported figures show, according to a new report.

Growing Gap Between Lab and Actual Emissions

Statistics reveals that PHEVs release just 19% less CO₂ than conventional petrol and diesel vehicles, based on analysis conducted by a advocacy organization. That contrasts sharply with laboratory estimates, which assumed a 75% reduction in emissions.

Researchers studied data from in-vehicle fuel consumption monitors of 800,000 vehicles sold in Europe from 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than official figures, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are decreasing,” said a senior analyst participating in the report. “This discrepancy is growing and poses a significant issue. Consequently, PHEVs pollute nearly as heavily as petrol vehicles.”

Key Reasons Driving the Discrepancy

Analysts attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in electric power compared to total distance. They determined that just a quarter of driving was completed in EV mode, while lab estimates suggested 84%.

Even, when operating in electric mode, pollution levels were well above official estimates. That occurred because EV motors were insufficiently powerful enough to operate independently, leading to engines burning gasoline for nearly one-third of the travel completed in EV mode.

Regulatory and Financial Consequences

According to estimates, the lowballing of PHEV CO2 output allowed several major carmaker companies to avoid more than €5bn in penalties from 2021 and 2023, by falsely easing adherence with EU fleet-average CO₂ targets.

Additionally, drivers of PHEVs would spend about €500 more annually in operating expenses than would be estimated under lab tests.

“The bold claims that automakers often promote about their PHEV cars are obviously far from the truth,” commented a transport analyst. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are little improved than standard gas and diesel vehicles in terms of energy use, CO₂ emissions, and operating expenses.”

Political Debate and Industry Pressure

Plug-in hybrid cars have lately been brought back into policy debates as automakers have pressed the EU to weaken CO₂ targets. A proposed ban on new internal combustion cars in 2035 has faced intense pressure from the automotive industry and resistance from EU countries with large car industries.

Some high-level politicians have proposed plug-in hybrids as a potential “compromise” solution to include in the legislation.

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

“The results show, beyond any doubt, that the difference in lab and actual PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or diesel vehicles,” the expert said. “All regulatory adjustments concerning PHEVs should be implemented with utmost caution and considering this data.”