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Plug-in hybrid cars emit almost 5x greater planet-heating pollution than lab-reported figures indicate, according to a recent analysis.

Widening Gap In Official and Actual CO2 Output

Statistics shows that PHEVs release only one-fifth less CO₂ than traditional gas and diesel vehicles, according to research carried out by a non-profit group. That contrasts significantly with lab tests, which assumed a 75% decrease in pollution.

Researchers examined information from onboard fuel consumption monitors of 800,000 vehicles sold in Europe between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, up from three and a half times in 2021.

“Actual CO2 output are rising, while official emissions are falling,” said a senior analyst involved in the report. “This gap is widening and creates a serious issue. Consequently, PHEVs pollute nearly as heavily as petrol cars.”

Primary Factors Driving the Discrepancy

Analysts attributed the majority of the difference to overestimates of the “electric driving share” – the percentage of kilometers travelled in battery mode relative to overall mileage. The team found that only a quarter of travel was done in EV mode, while official estimates suggested over four-fifths.

Additionally, when running in EV mode, emission levels were significantly higher than lab estimates. That occurred because EV motors were not strong enough to function alone, leading to engines using fossil fuels for nearly a third of the distance covered in EV mode.

Regulatory and Financial Implications

According to calculations, the underestimation of PHEV CO2 output allowed several major carmaker groups to escape over €5bn in penalties from 2021 and 2023, by falsely easing adherence with EU fleet-average CO₂ standards.

Furthermore, drivers of PHEVs would pay approximately €500 more per year in operating expenses than would be assumed under lab conditions.

“The bold statements that automakers often promote about their plug-in hybrid cars are obviously way off the truth,” stated a automotive expert. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the environment and cutting money. In reality, PHEVs are little better than regular gas and diesel cars in terms of energy use, CO₂ emissions, and running costs.”

Policy Discussion and Automotive Lobbying

Hybrid cars have lately been brought again into policy debates as carmakers have pressed the European Union to weaken CO₂ targets. A planned ban on sales of new internal combustion cars in 2035 has faced heavy lobbying from the automotive industry and opposition from EU countries with large car industries.

Several senior officials have proposed plug-in hybrids as a possible “flexibility” solution to include in the regulation.

One external energy policy expert, who was unaffiliated with the study, called the analysis a “highly valuable addition” after a long period in which parts of the car sector argued there was insufficient data to properly assess real-world CO2 output.

“The results show, without question, that the difference between lab and actual PHEV energy use and CO₂ emissions is significantly greater than for gasoline or diesel cars,” they stated. “Any regulatory changes regarding PHEVs should be implemented with utmost care and considering that data.”