Plug-in Hybrid electric Vehicles Pollute Almost as Heavily as Gasoline Vehicles, Study Finds

Plug-in hybrid cars release nearly five times more planet-heating emissions than official figures indicate, according to a new analysis.

Widening Discrepancy Between Lab and Real-World CO2 Output

Data reveals that PHEVs emit just one-fifth lower CO₂ than traditional petrol and diesel vehicles, according to research carried out by a advocacy organization. This differs sharply with lab tests, which assumed a three-quarters decrease in emissions.

Researchers studied information from onboard energy use meters of 800,000 cars sold in the EU between 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, increased from three and a half times in 2021.

“Actual emissions are increasing, while official emissions are falling,” stated a senior analyst involved in the report. “This gap is growing and poses a significant issue. As a result, PHEVs pollute almost as heavily as gasoline vehicles.”

Key Reasons Driving the Emissions Gap

Analysts attributed most of the difference to overestimates of the “utility factor” – the percentage of miles travelled in electric power compared to overall distance. The team found that only a quarter of travel was completed in EV mode, while lab assumptions assumed over four-fifths.

Additionally, when running in electric mode, emission amounts were well above lab projections. This occurred because electric motors were not strong enough to function independently, resulting to engines using gasoline for nearly one-third of the distance completed in EV mode.

Regulatory and Financial Implications

According to calculations, the underestimation of PHEV CO2 output allowed four large carmaker groups to avoid more than €5bn in fines between 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ targets.

Additionally, owners of PHEVs would pay approximately €500 extra annually in running costs than is estimated under laboratory conditions.

“The bold claims that manufacturers like to make about their plug-in hybrid vehicles are clearly far from the truth,” commented a automotive expert. “Buyers are being misled into thinking that by buying a PHEV, they are helping the environment and saving money. Actually, PHEVs are little improved than regular petrol and diesel vehicles in terms of energy use, CO₂ production, and running costs.”

Policy Discussion and Industry Lobbying

Plug-in hybrid cars have recently been drawn again into policy debates as carmakers have pressed the European Union to relax CO₂ standards. A proposed prohibition on new combustion engine vehicles in 2035 has faced heavy lobbying from the car sector and opposition from member states with significant automotive manufacturing.

Some high-level politicians have proposed PHEVs as a potential “flexibility” option to introduce in the legislation.

An independent energy policy specialist, who was not involved with the study, described the report a “very useful addition” after years in which segments of the car industry argued there was insufficient information to properly evaluate actual emissions.

“These findings show, beyond any doubt, that the gap in official and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or conventional vehicles,” the expert stated. “All regulatory adjustments regarding PHEVs should be made with extreme care and considering that evidence.”