Plug-in Hybrid electric Vehicles Pollute Almost as Much as Petrol Vehicles, Report Reveals

PHEVs release almost five times greater global warming emissions than official figures show, according to a new report.

Growing Gap In Official and Actual Emissions

Data shows that PHEVs release only 19% less CO₂ than conventional petrol and diesel cars, based on research carried out by a advocacy group. That differs significantly with laboratory tests, which assumed a three-quarters reduction in emissions.

Researchers studied data from in-vehicle energy use monitors of 800,000 cars registered in Europe from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than official figures, up from three and a half times in 2021.

“Real-world CO2 output are increasing, while lab-reported figures are decreasing,” said a lead analyst involved in the report. “That discrepancy is growing and creates a significant problem. As a result, PHEVs pollute nearly as heavily as gasoline vehicles.”

Primary Factors Behind the Emissions Gap

Analysts attributed the majority of the difference to overestimates of the “electric driving share” – the ratio of miles travelled in electric power compared to total mileage. They determined that only 27% of travel was done in electric mode, whereas lab assumptions assumed over four-fifths.

Even, when running in EV mode, emission amounts were significantly higher than official estimates. That happened because electric motors were not strong enough to operate independently, resulting to combustion motors using fossil fuels for almost one-third of the travel covered in EV mode.

Regulatory and Financial Implications

Based on estimates, the underestimation of PHEV CO2 output enabled several major carmaker groups to escape more than €5bn in penalties between 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ targets.

Additionally, owners of PHEVs could pay approximately €500 extra annually in operating costs than would be assumed under laboratory conditions.

“The bold statements that manufacturers often promote about their PHEV cars are obviously way off the mark,” commented a automotive expert. “Buyers are being misled into thinking that by buying a PHEV, they are helping the planet and saving costs. In reality, PHEVs are little better than standard petrol and diesel cars in terms of fuel use, CO₂ emissions, and running expenses.”

Policy Discussion and Automotive Pressure

Plug-in hybrid cars have recently been brought back into policy debates as carmakers have pressed the EU to weaken CO₂ targets. A proposed prohibition on new internal combustion cars in 2035 has faced heavy pressure from the automotive sector and resistance from EU countries with large car manufacturing.

Some senior politicians have proposed PHEVs as a possible “flexibility” option to include in the legislation.

One external energy policy expert, who was not involved with the study, described the report a “highly valuable addition” after a long period in which segments of the car industry argued there was insufficient information to properly evaluate actual CO2 output.

“These findings show, beyond any doubt, that the difference in lab and actual PHEV fuel consumption and CO₂ output is significantly greater than for petrol or diesel vehicles,” they stated. “Any policy changes concerning PHEVs should be implemented with utmost care and considering this evidence.”