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Plug-in hybrid cars produce almost 5x greater planet-heating pollution than official data indicate, according to a new report.

Widening Gap In Lab and Actual CO2 Output

Data shows that PHEVs emit only 19% less CO₂ than conventional petrol and diesel vehicles, based on research carried out by a non-profit group. That contrasts sharply with laboratory estimates, which assumed a three-quarters decrease in pollution.

Researchers examined data from onboard fuel consumption meters of 800,000 vehicles registered in the EU between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, increased from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported figures are falling,” stated a senior analyst involved in the report. “That gap is growing and creates a serious problem. As a result, PHEVs emit nearly as heavily as petrol vehicles.”

Key Factors Behind the Emissions Gap

Analysts attributed most of the difference to overestimates of the “utility factor” – the percentage of miles driven in battery mode relative to overall distance. They determined that just 27% of travel was done in EV mode, while official assumptions suggested over four-fifths.

Even, when running in electric mode, pollution amounts were well above official estimates. This occurred because electric motors were insufficiently powerful sufficient to function alone, resulting to engines using gasoline for almost one-third of the travel completed in electric mode.

Regulatory and Financial Consequences

Based on estimates, the lowballing of PHEV CO2 output enabled four major carmaker companies to avoid over €5bn in penalties between 2021 and 2023, by artificially easing adherence with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs would pay approximately €500 extra annually in running expenses than would be estimated under laboratory conditions.

“The strong claims that manufacturers often promote about their plug-in hybrid vehicles are obviously far from the mark,” commented a automotive expert. “Consumers are being misled into thinking that by buying a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are only slightly improved than regular petrol and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running expenses.”

Political Debate and Industry Lobbying

Plug-in hybrid cars have lately been drawn again into policy discussions as carmakers have lobbied the EU to relax CO₂ standards. A proposed prohibition on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the automotive sector and resistance from member states with significant car industries.

Several senior officials have proposed PHEVs as a possible “compromise” solution to include in the regulation.

One external energy economics expert, who was not involved with the research, called the report a “highly valuable contribution” after a long period in which segments of the car industry argued there was insufficient data to accurately evaluate real-world CO2 output.

“These findings show, without question, that the difference in official and real-world PHEV energy use and CO₂ output is much, much larger than for petrol or diesel cars,” the expert stated. “All policy adjustments concerning PHEVs should be made with extreme caution and considering that data.”