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Plug-in hybrid cars produce nearly five times more global warming pollution than lab-reported figures show, as per a new report.

Growing Discrepancy In Lab and Actual CO2 Output

Statistics reveals that PHEVs emit just 19% less CO₂ than conventional petrol and diesel vehicles, according to analysis carried out by a non-profit group. This differs significantly with laboratory tests, which suggested a three-quarters decrease in emissions.

Analysts examined data from in-vehicle energy use meters of 800,000 cars registered in the EU from 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, up from three and a half times in 2021.

“Real-world CO2 output are increasing, while lab-reported figures are decreasing,” said a lead researcher participating in the report. “This discrepancy is widening and poses a serious issue. As a result, PHEVs pollute almost as heavily as petrol cars.”

Key Factors Behind the Emissions Gap

Researchers linked the majority of the gap to inflated estimates of the “utility factor” – the ratio of miles driven in battery power relative to total distance. The team determined that just 27% of travel was done in electric mode, whereas official estimates assumed over four-fifths.

Even, when running in electric mode, emission levels were well above official estimates. That occurred because EV motors were not strong sufficient to function alone, resulting to engines burning gasoline for almost one-third of the travel completed in EV mode.

Policy and Financial Consequences

According to estimates, the lowballing of PHEV emissions enabled four large automaker groups to avoid over €5bn in fines between 2021 and 2023, by falsely easing compliance with EU fleet-average CO₂ standards.

Additionally, owners of PHEVs could pay about €500 more annually in operating expenses than would be estimated under lab conditions.

“The strong statements that automakers often promote about their PHEV cars are obviously way off the truth,” commented a automotive expert. “Consumers are being duped into believing that by buying a PHEV, they are helping the planet and cutting costs. In reality, PHEVs are little improved than regular petrol and diesel vehicles in terms of energy use, CO₂ emissions, and running expenses.”

Policy Discussion and Industry Pressure

Plug-in hybrid cars have recently been drawn again into policy discussions as carmakers have lobbied the European Union to relax CO₂ standards. A planned prohibition on new combustion engine cars in 2035 has faced intense pressure from the automotive sector and resistance from EU countries with large automotive manufacturing.

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

One independent energy economics specialist, who was not involved with the research, called the analysis a “very useful contribution” after years in which parts of the automotive industry argued there was insufficient information to properly assess real-world CO2 output.

“The results demonstrate, without question, that the gap between lab and real-world PHEV fuel consumption and CO₂ output is much, much larger than for petrol or conventional vehicles,” they said. “Any regulatory adjustments regarding PHEVs should be implemented with utmost caution and in the light of this data.”