Plug in Hybrid Vehicles Emit Nearly as Heavily as Gasoline Cars, Study Finds

PHEVs emit nearly five times more global warming pollution than lab-reported data show, according to a new analysis.

Widening Gap In Lab and Actual Emissions

Data shows that PHEVs release just one-fifth lower CO₂ than traditional gas and diesel vehicles, according to analysis conducted by a advocacy organization. This differs significantly with laboratory estimates, which assumed a 75% reduction in emissions.

Researchers examined information from onboard fuel consumption meters of 800,000 cars sold in the EU from 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official figures, up from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are decreasing,” said a senior analyst involved in the study. “That discrepancy is widening and poses a serious problem. Consequently, PHEVs emit almost as heavily as gasoline cars.”

Key Factors Driving the Discrepancy

Researchers attributed the majority of the gap to overestimates of the “utility factor” – the percentage of kilometers travelled in electric mode relative to total distance. They determined that just 27% of driving was completed in EV mode, while lab assumptions assumed over four-fifths.

Even, when running in electric mode, pollution amounts were well above official projections. This occurred because EV motors were insufficiently powerful enough to operate independently, leading to combustion motors using gasoline for nearly one-third of the travel completed in EV mode.

Regulatory and Economic Consequences

According to estimates, the lowballing of PHEV emissions allowed four major carmaker companies to avoid more than €5bn in fines from 2021 and 2023, by falsely easing compliance with EU fleet-average CO₂ targets.

Furthermore, owners of PHEVs would pay approximately €500 more per year in running expenses than is estimated under lab tests.

“The strong statements that manufacturers often promote about their plug-in hybrid cars are clearly way off the mark,” stated a transport expert. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the environment and cutting money. Actually, PHEVs are little better than standard gas and diesel vehicles in terms of fuel consumption, CO₂ production, and running costs.”

Political Debate and Automotive Pressure

Hybrid cars have recently been brought back into policy discussions as automakers have lobbied the European Union to weaken CO₂ standards. A planned ban on sales of new combustion engine cars in 2035 has faced heavy lobbying from the automotive sector and resistance from EU countries with large car industries.

Some high-level politicians have proposed PHEVs as a potential “flexibility” option to introduce in the legislation.

An independent 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 automotive industry claimed there was too little data to accurately assess real-world CO2 output.

“The results show, beyond any doubt, that the difference in lab and actual PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or diesel cars,” the expert said. “All policy changes regarding PHEVs should be implemented with utmost caution and considering that data.”