Plug-in Hybrid Cars Emit Almost as Much as Gasoline Cars, Report Reveals

PHEVs release nearly five times greater global warming pollution than lab-reported figures indicate, as per a new report.

Growing Discrepancy In Lab and Real-World Emissions

Data reveals that PHEVs release just one-fifth lower CO₂ than conventional petrol and diesel cars, based on research conducted by a non-profit group. This contrasts sharply with lab estimates, which suggested a three-quarters reduction in emissions.

Researchers examined information from in-vehicle fuel consumption monitors of eight hundred thousand vehicles registered in Europe between 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are decreasing,” stated a lead researcher involved in the study. “This gap is growing and creates a significant issue. Consequently, PHEVs pollute almost as much as petrol cars.”

Key Reasons Behind the Discrepancy

Researchers attributed most of the difference to inflated estimates of the “utility factor” – the ratio of miles travelled in battery power relative to total mileage. They found that only a quarter of driving was completed in EV mode, whereas official estimates assumed 84%.

Additionally, when operating in electric mode, emission levels were well above lab estimates. This happened because electric motors were insufficiently powerful sufficient to function independently, leading to engines burning gasoline for almost a third of the travel completed in EV mode.

Policy and Financial Consequences

Based on estimates, the lowballing of PHEV CO2 output allowed several large carmaker groups to escape over €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ targets.

Additionally, drivers of PHEVs could pay about €500 extra annually in running costs than would be assumed under laboratory conditions.

“The strong statements that automakers often promote about their PHEV vehicles are clearly way off the mark,” commented a transport analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the environment and cutting money. Actually, PHEVs are only slightly improved than regular gas and diesel cars in terms of energy use, CO₂ production, and operating costs.”

Policy Discussion and Automotive Pressure

Hybrid vehicles have recently been drawn again into political debates as automakers have lobbied the EU to relax CO₂ standards. A planned prohibition on new combustion engine cars in 2035 has faced heavy pressure from the car sector and resistance from EU countries with significant automotive manufacturing.

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

One external energy economics specialist, who was unaffiliated with the research, called the analysis a “highly valuable addition” after a long period in which parts of the automotive industry claimed there was too little data to accurately assess real-world CO2 output.

“The results demonstrate, without question, that the gap between lab and actual PHEV energy use and CO₂ emissions is much, much greater than for gasoline or conventional cars,” the expert said. “Any policy changes regarding PHEVs should be made with extreme caution and in the light of that data.”