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Plug-in hybrid electric vehicles release almost five times more global warming pollution than lab-reported figures show, as per a new analysis.

Widening Discrepancy Between Lab and Actual Emissions

Data shows that PHEVs release just one-fifth lower CO₂ than conventional gas and diesel cars, according to research conducted by a non-profit group. That differs significantly with lab estimates, which suggested a three-quarters decrease in pollution.

Analysts studied information from onboard fuel consumption meters of eight hundred thousand cars registered in the EU from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab figures, increased from 3.5 times in 2021.

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

Key Factors Driving the Emissions Gap

Analysts linked most of the gap to inflated estimates of the “utility factor” – the ratio of kilometers travelled in electric mode compared to overall mileage. They determined that just 27% of driving was completed in EV mode, whereas lab estimates suggested over four-fifths.

Even, when running in electric 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 a third of the travel covered in EV mode.

Policy and Financial Implications

According to estimates, the underestimation of PHEV CO2 output enabled several major carmaker companies to escape over €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ targets.

Furthermore, drivers of PHEVs would pay approximately €500 more annually in operating costs than is assumed under laboratory tests.

“The strong claims that manufacturers often promote about their plug-in hybrid vehicles are clearly far from the mark,” commented a transport analyst. “Buyers are being duped into thinking that by buying a PHEV, they are helping the environment and cutting money. Actually, PHEVs are only slightly improved than regular petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and running costs.”

Policy Discussion and Automotive Pressure

Plug-in hybrid vehicles have lately been brought again into policy discussions 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 automotive sector and resistance from EU countries with large car industries.

Several senior officials have proposed PHEVs as a possible “compromise” solution to include in the legislation.

One independent energy economics expert, who was unaffiliated with the study, described the analysis a “very useful addition” after a long period in which parts of the car sector argued there was insufficient information to accurately assess real-world CO2 output.

“The results show, beyond any doubt, that the difference between lab and actual PHEV fuel consumption and CO₂ output is significantly larger than for petrol or diesel cars,” the expert stated. “Any regulatory adjustments regarding PHEVs should be made with utmost caution and considering this evidence.”