Plug-in Hybrid Vehicles Emit Almost as Heavily as Petrol Vehicles, Study Finds

PHEVs produce nearly 5x more planet-heating emissions than official figures show, according to a new report.

Growing Gap Between Official and Actual Emissions

Data reveals that PHEVs release only one-fifth less CO₂ than conventional gas and diesel cars, according to analysis carried out by a non-profit group. That contrasts sharply with lab estimates, which assumed a three-quarters decrease in emissions.

Analysts studied data from onboard fuel consumption monitors of 800,000 vehicles sold in the EU from 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, up from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported emissions are decreasing,” stated a senior researcher involved in the report. “This discrepancy is growing and creates a significant problem. As a result, PHEVs pollute almost as heavily as gasoline vehicles.”

Key Reasons Driving the Emissions Gap

Researchers attributed the majority of the difference to inflated estimates of the “utility factor” – the percentage of kilometers driven in electric power compared to overall mileage. The team determined that only 27% of travel was done in EV mode, whereas lab estimates assumed 84%.

Additionally, when operating in EV mode, pollution levels were well above lab estimates. That happened because EV motors were insufficiently powerful enough to function independently, resulting to engines using fossil fuels for nearly one-third of the travel completed in EV mode.

Regulatory and Financial Implications

Based on estimates, the lowballing of PHEV CO2 output allowed several large automaker companies to escape over €5bn in penalties from 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ targets.

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

“The bold claims that manufacturers often promote about their PHEV cars are obviously way off the mark,” stated a automotive expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are helping the environment and cutting money. Actually, PHEVs are little improved than standard petrol and diesel vehicles in terms of energy use, CO₂ production, and operating expenses.”

Policy Debate and Industry Lobbying

Hybrid vehicles have lately been brought back into policy discussions as automakers have lobbied the EU to relax CO₂ targets. A planned ban on new internal combustion cars in 2035 has faced intense lobbying from the car sector and opposition from member states with significant car manufacturing.

Several senior politicians have proposed PHEVs as a potential “flexibility” solution to include in the legislation.

An external energy policy expert, who was not involved with the research, called the report a “very useful contribution” after years in which parts of the automotive sector claimed there was insufficient data to accurately assess real-world emissions.

“The results demonstrate, beyond any doubt, that the gap between lab and real-world PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or diesel vehicles,” they stated. “Any policy adjustments concerning PHEVs should be implemented with utmost care and in the light of that data.”