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Plug-in hybrid cars emit almost five times greater planet-heating pollution than lab-reported data show, according to a recent report.

Growing Discrepancy In Lab and Actual CO2 Output

Data reveals that PHEVs release only 19% less CO₂ than conventional gas and diesel cars, according to analysis conducted by a non-profit organization. This contrasts sharply with lab tests, which suggested a 75% reduction in pollution.

Analysts studied information from onboard fuel consumption meters of 800,000 cars sold in the EU between 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, up from three and a half times in 2021.

“Actual CO2 output are rising, while official emissions are decreasing,” stated a lead analyst involved in the study. “That discrepancy is widening and creates a serious issue. As a result, PHEVs pollute almost as heavily as gasoline cars.”

Primary Reasons Driving the Discrepancy

Analysts linked the majority of the gap to overestimates of the “electric driving share” – the percentage of kilometers driven in battery power relative to overall distance. The team determined that only 27% of travel was completed in electric mode, while lab assumptions suggested over four-fifths.

Additionally, when operating in EV mode, pollution levels were well above lab estimates. This happened because electric motors were insufficiently powerful enough to operate alone, resulting to combustion motors using fossil fuels for nearly one-third of the distance completed in electric mode.

Policy and Financial Implications

According to estimates, the lowballing of PHEV CO2 output enabled four large carmaker companies to avoid more than €5bn in penalties from 2021 and 2023, by artificially easing compliance with EU average fleet CO₂ targets.

Additionally, owners of PHEVs would pay about €500 extra annually in running costs than is estimated under laboratory conditions.

“The strong claims that automakers like to make about their PHEV cars are clearly far from the mark,” stated a automotive expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are little better than regular gas and diesel cars in terms of energy consumption, CO₂ production, and running costs.”

Political Debate and Industry Pressure

Plug-in hybrid vehicles have lately been brought again into policy debates as carmakers have lobbied the European Union to weaken CO₂ targets. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the automotive sector and opposition from member states with large car industries.

Some senior politicians have suggested plug-in hybrids as a possible “flexibility” solution to introduce in the legislation.

An external 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 car sector claimed there was too little data to accurately evaluate actual emissions.

“The results demonstrate, beyond any doubt, that the difference in official and actual PHEV energy use and CO₂ emissions is much, much larger than for petrol or diesel cars,” the expert stated. “Any regulatory adjustments regarding PHEVs should be implemented with utmost caution and in the light of this data.”