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Plug-in hybrid cars emit almost 5x greater global warming pollution than official figures show, according to a recent analysis.

Widening Gap In Lab and Real-World CO2 Output

Data reveals that PHEVs emit just 19% less CO₂ than traditional petrol and diesel cars, based on research conducted by a non-profit group. This contrasts sharply with laboratory estimates, which suggested a 75% reduction in emissions.

Analysts examined data from in-vehicle fuel consumption monitors of eight hundred thousand vehicles sold in Europe between 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official figures are falling,” said a senior researcher participating in the report. “This discrepancy is growing and poses a significant issue. Consequently, PHEVs emit nearly as heavily as gasoline cars.”

Key Reasons Driving the Emissions Gap

Analysts linked most of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in electric mode compared to total distance. They found that just 27% of driving was completed in electric mode, whereas official assumptions assumed 84%.

Additionally, when operating in electric mode, pollution amounts were significantly higher than lab projections. That happened because EV motors were insufficiently powerful enough to function alone, leading to engines using fossil fuels for almost a third of the travel completed in electric mode.

Policy and Financial Consequences

Based on calculations, the underestimation of PHEV CO2 output enabled several large automaker companies to avoid more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs would spend approximately €500 extra annually in operating expenses than would be estimated under laboratory tests.

“The strong statements that manufacturers often promote about their plug-in hybrid vehicles are obviously far from the mark,” stated a automotive expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are only slightly better than standard gas and diesel vehicles in terms of fuel use, CO₂ emissions, and running costs.”

Policy Debate and Automotive Pressure

Plug-in hybrid cars have lately been drawn back into policy debates as automakers have pressed the European Union to relax CO₂ targets. A planned ban on new combustion engine cars in 2035 has faced heavy lobbying from the car sector and opposition from EU countries with significant car manufacturing.

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

An independent energy policy expert, who was not involved with the research, called the analysis a “very useful contribution” after a long period in which parts of the automotive sector claimed there was too little information to properly assess real-world CO2 output.

“The results demonstrate, without question, that the gap in lab and real-world PHEV energy use and CO₂ output is significantly larger than for petrol or diesel cars,” they stated. “Any regulatory adjustments regarding PHEVs should be made with extreme care and in the light of that evidence.”