Plug-in Hybrid Cars Emit Nearly as Much as Gasoline Cars, Study Finds

Plug-in hybrid cars produce almost 5x greater global warming pollution than official data show, according to a recent report.

Growing Discrepancy In Lab and Real-World CO2 Output

Statistics shows that PHEVs emit just one-fifth lower CO₂ than traditional petrol and diesel cars, based on analysis carried out by a non-profit organization. That contrasts significantly with lab tests, which assumed a 75% reduction in emissions.

Analysts examined information from in-vehicle fuel consumption monitors of 800,000 cars sold in the EU from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported figures are decreasing,” stated a senior analyst participating in the report. “That gap is growing and creates a significant issue. Consequently, PHEVs pollute almost as heavily as petrol cars.”

Primary Reasons Driving the Emissions Gap

Researchers linked most of the gap to overestimates of the “utility factor” – the ratio of miles driven in electric mode relative to overall mileage. The team determined that just 27% of travel was completed in electric mode, whereas lab estimates suggested 84%.

Additionally, when operating in EV mode, pollution levels were significantly higher than lab projections. That occurred because electric motors were not strong enough to function independently, leading to combustion motors using gasoline for nearly one-third of the travel completed in EV mode.

Policy and Economic Consequences

According to calculations, the lowballing of PHEV CO2 output enabled four major automaker groups to escape more than €5bn in fines from 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs would spend about €500 more annually in operating costs than is assumed under laboratory conditions.

“The bold statements that manufacturers often promote about their PHEV cars are clearly far from the truth,” stated a transport analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are helping the environment and cutting money. Actually, PHEVs are only slightly better than regular gas and diesel cars in terms of fuel use, CO₂ production, and running costs.”

Policy Debate and Automotive Pressure

Plug-in hybrid vehicles have lately been drawn back into policy discussions as automakers have pressed the European Union to weaken CO₂ targets. A planned ban on new internal combustion cars in 2035 has faced intense lobbying from the automotive industry and opposition from EU countries with significant automotive manufacturing.

Some senior officials have proposed PHEVs as a potential “flexibility” option to introduce in the legislation.

An independent energy economics specialist, who was not involved with the study, described the analysis a “very useful addition” after a long period in which segments of the car sector argued there was insufficient data to accurately assess actual CO2 output.

“The results demonstrate, without question, that the difference between official and actual PHEV fuel consumption and CO₂ output is significantly greater than for petrol or conventional cars,” the expert stated. “Any regulatory adjustments regarding PHEVs should be implemented with extreme care and in the light of that evidence.”