Plug-in Hybrid electric Cars Emit Almost as Heavily as Gasoline Vehicles, Report Finds

Plug-in hybrid cars produce almost five times more planet-heating pollution than lab-reported figures show, according to a recent report.

Growing Discrepancy Between Lab and Actual Emissions

Data shows that PHEVs release only one-fifth lower CO₂ than traditional gas and diesel cars, based on analysis conducted by a advocacy group. That contrasts sharply with lab estimates, which assumed a 75% decrease in emissions.

Researchers examined data from onboard energy use meters of eight hundred thousand vehicles registered in Europe from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, up from 3.5 times in 2021.

“Real-world CO2 output are rising, while official figures are decreasing,” said a senior analyst participating in the report. “This discrepancy is growing and poses a serious issue. Consequently, PHEVs emit almost as much as petrol cars.”

Key Factors Behind the Discrepancy

Researchers linked the majority of the gap to inflated estimates of the “utility factor” – the ratio of kilometers driven in electric mode relative to total mileage. They determined that only 27% of travel was completed in electric mode, whereas official estimates suggested 84%.

Even, when operating in electric mode, emission levels were well above official projections. This occurred because electric motors were not strong enough to function independently, leading to engines using gasoline for almost one-third of the distance completed in EV mode.

Regulatory and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output enabled several large carmaker groups to escape over €5bn in fines from 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ targets.

Additionally, owners of PHEVs would pay approximately €500 extra per year in running costs than is assumed under laboratory tests.

“The strong claims that automakers like to make about their PHEV vehicles are clearly way off the mark,” commented a automotive expert. “Consumers are being misled into thinking that by buying a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are only slightly improved than regular gas and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating costs.”

Policy Discussion and Industry Pressure

Plug-in hybrid cars have lately been drawn back into policy debates as automakers have lobbied the European Union to relax CO₂ targets. A proposed prohibition on sales of new combustion engine cars in 2035 has faced intense lobbying from the automotive sector and resistance from member states with large car industries.

Some senior officials have suggested plug-in hybrids as a possible “flexibility” solution to include in the legislation.

An external energy policy expert, who was not involved with the research, described the analysis a “highly valuable addition” after a long period in which parts of the car sector argued there was too little data to properly evaluate actual emissions.

“The results show, beyond any doubt, that the gap in official and actual PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or conventional vehicles,” they said. “Any policy changes concerning PHEVs should be made with extreme caution and in the light of that evidence.”