Plug-in Hybrid Cars Emit Nearly as Heavily as Gasoline Cars, Study Reveals

PHEVs emit almost 5x more planet-heating pollution than lab-reported data indicate, according to a new analysis.

Widening Discrepancy Between Lab and Actual CO2 Output

Data reveals that PHEVs emit just one-fifth less CO₂ than traditional petrol and diesel vehicles, according to analysis conducted by a non-profit group. This contrasts significantly with lab tests, which assumed a three-quarters reduction in pollution.

Analysts studied information from onboard energy use monitors of eight hundred thousand vehicles sold in the EU between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while official emissions are falling,” said a senior researcher participating in the report. “That discrepancy is growing and creates a significant issue. Consequently, PHEVs pollute nearly as much as gasoline cars.”

Key Factors Driving the Emissions Gap

Analysts linked most of the difference to overestimates of the “utility factor” – the ratio of miles travelled in electric mode relative to overall distance. They determined that only 27% of driving was done in EV mode, while lab estimates assumed over four-fifths.

Even, when operating in electric mode, pollution levels were significantly higher than official projections. That happened because electric motors were insufficiently powerful sufficient to function independently, resulting to combustion motors using gasoline for nearly one-third of the travel completed in EV mode.

Regulatory and Economic Implications

Based on estimates, the lowballing of PHEV CO2 output enabled several major automaker companies to avoid more than €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs would pay about €500 more per year in running costs than would be estimated under laboratory conditions.

“The strong statements that automakers like to make about their PHEV cars are clearly far from the truth,” commented a transport analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are helping the planet and saving costs. Actually, PHEVs are little better than standard gas and diesel cars in terms of fuel consumption, CO₂ production, and operating costs.”

Policy Discussion and Automotive Pressure

Plug-in hybrid vehicles have recently been brought back into political debates as automakers have pressed the EU to relax CO₂ targets. A planned ban on new combustion engine vehicles in 2035 has faced intense pressure from the automotive sector and opposition from member states with significant car industries.

Some high-level officials have suggested plug-in hybrids as a potential “flexibility” option to include in the legislation.

An external energy policy expert, who was not involved with the study, described the report a “very useful contribution” after years in which segments of the automotive industry claimed there was insufficient information to properly assess real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the gap in lab and actual PHEV energy use and CO₂ emissions is much, much greater than for gasoline or conventional vehicles,” they said. “Any regulatory changes concerning PHEVs should be implemented with extreme caution and considering that data.”