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Plug-in hybrid cars emit nearly five times more global warming pollution than lab-reported data show, as per a new analysis.

Growing Discrepancy Between Lab and Actual Emissions

Data shows that PHEVs emit only one-fifth less CO₂ than traditional petrol and diesel cars, according to research carried out by a non-profit organization. This contrasts sharply with laboratory tests, which assumed a 75% reduction in emissions.

Researchers examined data from onboard energy use meters of eight hundred thousand cars sold in Europe from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab estimates, increased from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are decreasing,” said a senior researcher participating in the study. “This gap is widening and creates a serious problem. As a result, PHEVs emit nearly as much as petrol vehicles.”

Key Factors Driving the Discrepancy

Researchers attributed most of the gap to inflated estimates of the “utility factor” – the ratio of kilometers travelled in battery mode relative to total distance. The team found that only a quarter of driving was done in EV mode, while lab estimates suggested 84%.

Additionally, when operating in electric mode, pollution amounts were well above official projections. This occurred because EV motors were not strong enough to operate alone, resulting to combustion motors burning gasoline for nearly one-third of the distance completed in EV mode.

Regulatory and Financial Implications

Based on calculations, the underestimation of PHEV emissions allowed several major automaker groups to avoid more than €5bn in penalties from 2021 and 2023, by falsely easing adherence with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could pay about €500 extra per year in running costs than is estimated under lab conditions.

“The bold statements that automakers often promote about their plug-in hybrid vehicles are obviously far from the truth,” commented a automotive expert. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are only slightly improved than regular gas and diesel cars in terms of fuel use, CO₂ production, and operating costs.”

Policy Discussion and Automotive Pressure

Plug-in hybrid cars have lately been brought again into political debates as automakers have pressed the EU to relax CO₂ targets. A proposed prohibition on new combustion engine cars in 2035 has faced intense lobbying from the car sector and resistance from member states with large automotive manufacturing.

Some high-level politicians have suggested PHEVs as a possible “flexibility” solution to introduce in the regulation.

One external energy economics specialist, who was not involved with the study, called the analysis a “highly valuable contribution” after years in which parts of the car industry argued there was insufficient information to properly assess actual CO2 output.

“The results show, without question, that the gap in official and actual PHEV energy use and CO₂ output is significantly larger than for petrol or conventional vehicles,” they stated. “All regulatory changes regarding PHEVs should be made with extreme care and in the light of this data.”