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Plug-in hybrid cars release nearly five times greater planet-heating emissions than lab-reported data indicate, as per a recent report.

Growing Discrepancy Between Lab and Real-World CO2 Output

Data reveals that PHEVs release only one-fifth less CO₂ than conventional petrol and diesel vehicles, based on research carried out by a advocacy organization. This differs sharply with laboratory estimates, which assumed a 75% reduction in emissions.

Researchers examined data from in-vehicle fuel consumption meters of 800,000 cars sold in the EU from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, up from three and a half times in 2021.

“Actual CO2 output are increasing, while official emissions are decreasing,” said a lead researcher involved in the report. “This discrepancy is growing and creates a significant issue. As a result, PHEVs emit almost as much as petrol cars.”

Primary Reasons Driving the Emissions Gap

Analysts attributed most of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers driven in battery power relative to total mileage. They determined that just 27% of driving was completed in electric mode, while official assumptions suggested 84%.

Additionally, when running in EV mode, pollution levels were well above lab projections. That occurred because electric motors were not strong enough to operate independently, leading to combustion motors using gasoline for nearly a third of the distance completed in EV mode.

Regulatory and Financial Consequences

Based on estimates, the underestimation of PHEV CO2 output enabled four major carmaker groups to avoid over €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would pay approximately €500 more per year in operating expenses than would be assumed under laboratory conditions.

“The strong claims that manufacturers often promote about their PHEV vehicles are clearly way off the truth,” stated a automotive analyst. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating costs.”

Policy Debate and Automotive Lobbying

Plug-in hybrid cars have lately been drawn again into political debates as carmakers have pressed the European Union to weaken CO₂ standards. A planned ban on sales of new combustion engine vehicles in 2035 has faced intense pressure from the car industry and resistance from EU countries with significant car industries.

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

An external energy economics expert, who was unaffiliated with the study, described the report a “very useful contribution” after a long period in which segments of the automotive sector claimed there was insufficient data to accurately assess actual CO2 output.

“These findings show, without question, that the difference in official and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or conventional cars,” they said. “Any regulatory changes concerning PHEVs should be made with utmost care and considering this data.”