Plug in Hybrid Vehicles Pollute Almost as Much as Petrol Vehicles, Study Finds

PHEVs produce almost 5x more planet-heating pollution than lab-reported figures indicate, according to a recent analysis.

Growing Discrepancy Between Lab and Real-World Emissions

Data reveals that PHEVs release just 19% lower CO₂ than conventional petrol and diesel vehicles, based on analysis carried out by a non-profit group. This differs significantly with lab estimates, which assumed a three-quarters reduction in pollution.

Researchers studied data from in-vehicle fuel consumption monitors of 800,000 cars sold in the EU between 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, increased from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported emissions are decreasing,” said a lead analyst involved in the report. “This gap is growing and poses a serious issue. Consequently, PHEVs emit nearly as heavily as petrol cars.”

Key Factors Driving the Discrepancy

Analysts attributed the majority of the gap to inflated estimates of the “electric driving share” – the ratio of miles driven in battery mode relative to total mileage. The team determined that only 27% of driving was done in electric mode, while official assumptions assumed over four-fifths.

Even, when running in EV mode, pollution levels were well above lab estimates. This occurred because electric motors were not strong enough to operate independently, resulting to combustion motors burning gasoline for nearly a third of the travel covered in electric mode.

Regulatory and Financial Consequences

According to calculations, the underestimation of PHEV emissions enabled four large carmaker groups to escape over €5bn in fines from 2021 and 2023, by artificially easing compliance with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs could spend approximately €500 more per year in running expenses than is estimated under lab conditions.

“The bold statements that manufacturers often promote about their plug-in hybrid vehicles are obviously way off the truth,” commented a automotive expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and saving costs. Actually, PHEVs are only slightly better than regular gas and diesel vehicles in terms of energy use, CO₂ emissions, and operating costs.”

Policy Discussion and Automotive Pressure

Hybrid vehicles have recently been drawn back into political debates as automakers have lobbied the European Union to relax CO₂ targets. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the car sector and opposition from EU countries with large automotive industries.

Several high-level politicians have proposed PHEVs as a potential “flexibility” solution to introduce in the regulation.

An external energy economics specialist, who was not involved with the study, described the analysis a “very useful addition” after years in which parts of the car sector argued there was too little information to properly evaluate real-world emissions.

“These findings show, without question, that the gap in official and actual PHEV energy use and CO₂ output is significantly greater than for gasoline or diesel vehicles,” they said. “Any regulatory changes concerning PHEVs should be made with extreme caution and considering this data.”