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PHEVs release almost five times more planet-heating emissions than official figures show, as per a new analysis.

Growing Discrepancy In Lab and Actual CO2 Output

Statistics reveals that PHEVs emit only 19% less CO₂ than conventional petrol and diesel cars, according to analysis carried out by a non-profit organization. That differs sharply with lab estimates, which assumed a three-quarters reduction in emissions.

Researchers examined data from in-vehicle energy use meters of eight hundred thousand vehicles sold in the EU from 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab estimates, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while official emissions are falling,” said a senior researcher participating in the study. “This gap is growing and poses a significant issue. Consequently, PHEVs pollute nearly as much as petrol vehicles.”

Key Reasons Driving the Discrepancy

Analysts attributed the majority of the difference to overestimates of the “electric driving share” – the ratio of kilometers driven in battery mode relative to total distance. They determined that just 27% of travel was done in EV mode, while official assumptions assumed over four-fifths.

Even, when operating in EV mode, emission levels were significantly higher than lab estimates. This occurred because electric motors were insufficiently powerful sufficient to operate independently, leading to engines burning fossil fuels for nearly one-third of the distance completed in electric mode.

Policy and Financial Consequences

Based on estimates, the underestimation of PHEV CO2 output allowed four large automaker companies to escape over €5bn in fines from 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs could spend about €500 extra per year in operating expenses than would be assumed under lab conditions.

“The strong claims that manufacturers often promote about their plug-in hybrid cars are obviously far from the truth,” commented a automotive analyst. “Buyers are being misled into thinking that by buying a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are only slightly better than regular petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and operating costs.”

Policy Debate and Automotive Pressure

Plug-in hybrid cars have lately been brought back into policy discussions as carmakers have pressed the EU to relax CO₂ standards. A planned prohibition on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the car industry and resistance from EU countries with significant automotive manufacturing.

Some high-level politicians have suggested plug-in hybrids as a possible “flexibility” solution to introduce in the regulation.

One external energy policy expert, who was not involved with the study, described the report a “highly valuable contribution” after a long period in which segments of the automotive industry argued there was insufficient information to accurately assess actual emissions.

“The results demonstrate, without question, that the difference between lab and real-world PHEV energy use and CO₂ output is much, much greater than for gasoline or conventional vehicles,” they stated. “Any policy changes concerning PHEVs should be implemented with utmost caution and in the light of that data.”