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Plug-in hybrid electric vehicles emit almost five times greater global warming emissions than lab-reported data indicate, according to a new analysis.

Widening Discrepancy In Official and Actual Emissions

Statistics shows that PHEVs release just 19% less CO₂ than conventional gas and diesel cars, according to analysis carried out by a non-profit organization. This differs sharply with lab estimates, which suggested a 75% reduction in pollution.

Analysts studied data from in-vehicle energy use meters of 800,000 vehicles registered in the EU from 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were nearly five times greater than official estimates, increased from 3.5 times in 2021.

“Actual emissions are rising, while official emissions are decreasing,” stated a senior analyst participating in the report. “This discrepancy is growing and creates a serious issue. Consequently, PHEVs pollute nearly as heavily as gasoline cars.”

Key Reasons Driving the Emissions Gap

Researchers attributed most of the difference to overestimates of the “utility factor” – the percentage of kilometers driven in battery power compared to total mileage. They found that only a quarter of driving was completed in electric mode, whereas lab estimates assumed 84%.

Additionally, when running in electric mode, emission amounts were significantly higher than lab projections. That happened because EV motors were not strong sufficient to operate alone, resulting to engines using gasoline for almost a third of the distance completed in electric mode.

Regulatory and Financial Implications

According to calculations, the lowballing of PHEV CO2 output enabled four large automaker groups to avoid over €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could spend about €500 more per year in running expenses than is assumed under laboratory conditions.

“The bold claims that automakers often promote about their PHEV vehicles are obviously way off the truth,” stated a automotive analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are only slightly improved than standard gas and diesel cars in terms of fuel consumption, CO₂ emissions, and running costs.”

Political Discussion and Automotive Lobbying

Hybrid vehicles have lately been brought back into policy discussions as carmakers have pressed the European Union to relax CO₂ standards. A planned prohibition on sales of new internal combustion cars in 2035 has faced intense lobbying from the automotive sector and resistance from member states with large automotive manufacturing.

Several senior officials have suggested plug-in hybrids as a potential “compromise” solution to include in the legislation.

An independent energy economics expert, who was not involved with the research, described the report a “highly valuable contribution” after a long period in which segments of the automotive sector argued there was insufficient data to properly assess real-world CO2 output.

“The results demonstrate, beyond any doubt, that the gap between lab and actual PHEV energy use and CO₂ output is much, much larger than for gasoline or conventional cars,” they said. “All policy changes concerning PHEVs should be implemented with utmost caution and considering that data.”