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Plug-in hybrid cars release nearly five times more planet-heating emissions than official figures show, as per a new report.

Growing Discrepancy Between Lab and Actual Emissions

Data shows that PHEVs release only one-fifth lower CO₂ than traditional gas and diesel cars, according to research carried out by a non-profit organization. This differs significantly with laboratory tests, which assumed a three-quarters reduction in emissions.

Researchers studied information from in-vehicle energy use meters of 800,000 cars registered in the EU from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, up from 3.5 times in 2021.

“Real-world emissions are increasing, while official emissions are falling,” stated a senior analyst participating in the study. “That gap is widening and creates a significant issue. Consequently, PHEVs pollute almost as heavily as petrol cars.”

Primary Reasons Driving the Emissions Gap

Researchers attributed the majority of the difference to inflated estimates of the “utility factor” – the percentage of miles travelled in electric power compared to total mileage. The team determined that only 27% of driving was completed in electric mode, while lab assumptions suggested 84%.

Additionally, when running in electric mode, pollution amounts were well above lab estimates. This happened because EV motors were not strong sufficient to function independently, resulting to engines burning fossil fuels for nearly one-third of the travel covered in electric mode.

Policy and Economic Implications

Based on calculations, the lowballing of PHEV CO2 output allowed several large automaker companies to avoid over €5bn in penalties between 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs could pay about €500 extra per year in running expenses than is estimated under lab conditions.

“The bold statements that automakers often promote about their PHEV cars are clearly way off the mark,” commented a automotive analyst. “Buyers are being misled into believing that by buying a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are little better than regular gas and diesel cars in terms of fuel consumption, CO₂ emissions, and running costs.”

Political Discussion and Industry Pressure

Plug-in hybrid vehicles have recently been brought back into political debates as automakers have lobbied the EU to relax CO₂ targets. A planned prohibition on new internal combustion cars in 2035 has faced heavy pressure from the car sector and resistance from EU countries with significant car manufacturing.

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

One independent energy economics expert, who was not involved with the research, described the analysis a “highly valuable contribution” after years in which parts of the automotive industry claimed there was insufficient data to accurately evaluate real-world CO2 output.

“These findings demonstrate, without question, that the gap between official and real-world PHEV fuel consumption and CO₂ emissions is significantly larger than for petrol or conventional vehicles,” they stated. “Any policy adjustments regarding PHEVs should be implemented with utmost care and considering that evidence.”