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Plug-in hybrid electric vehicles emit nearly five times more planet-heating pollution than official figures indicate, according to a recent analysis.

Growing Discrepancy Between Official and Actual Emissions

Data reveals that PHEVs release only one-fifth lower CO₂ than traditional gas and diesel vehicles, according to analysis conducted by a non-profit group. This differs significantly with laboratory tests, which suggested a 75% reduction in emissions.

Analysts examined data from onboard fuel consumption monitors of eight hundred thousand cars sold in Europe between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, up from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are falling,” stated a senior analyst participating in the report. “This discrepancy is widening and poses a significant issue. Consequently, PHEVs pollute almost as heavily as gasoline cars.”

Primary Reasons Driving the Discrepancy

Researchers attributed most of the gap to inflated estimates of the “utility factor” – the percentage of kilometers driven in electric power compared to overall mileage. They found that just 27% of driving was completed in EV mode, while lab assumptions suggested over four-fifths.

Even, when operating in EV mode, emission levels were well above lab estimates. That occurred because EV motors were not strong enough to operate independently, leading to engines using gasoline for nearly a third of the travel completed in EV mode.

Regulatory and Financial Consequences

Based on calculations, the underestimation of PHEV CO2 output enabled several large carmaker companies to escape more than €5bn in penalties from 2021 and 2023, by artificially easing adherence with European Union fleet-average CO₂ standards.

Furthermore, owners of PHEVs would pay about €500 more per year in operating costs than would be estimated under laboratory conditions.

“The bold statements that automakers like to make about their PHEV vehicles are clearly far from the truth,” stated a automotive expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and saving costs. In reality, PHEVs are little improved than standard petrol and diesel cars in terms of fuel consumption, CO₂ production, and operating expenses.”

Political Debate and Automotive Pressure

Plug-in hybrid cars have recently been brought again into political debates as carmakers have lobbied the European Union to relax CO₂ standards. A proposed prohibition on sales of new internal combustion cars in 2035 has faced heavy pressure from the car industry and opposition from EU countries with large car manufacturing.

Some senior politicians have proposed plug-in hybrids as a potential “flexibility” solution to introduce in the regulation.

One external energy policy specialist, who was not involved with the research, described the analysis a “highly valuable addition” after a long period in which parts of the car industry argued there was insufficient information to accurately evaluate real-world emissions.

“The results demonstrate, without question, that the gap between official and actual PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or diesel cars,” they said. “Any regulatory adjustments concerning PHEVs should be made with utmost caution and considering that evidence.”