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PHEVs emit nearly 5x more planet-heating pollution than official data show, as per a recent analysis.

Growing Gap Between Official and Actual Emissions

Data shows that PHEVs emit just one-fifth less CO₂ than conventional gas and diesel vehicles, according to research conducted by a non-profit group. That contrasts sharply with laboratory tests, which suggested a three-quarters reduction in emissions.

Analysts studied data from in-vehicle fuel consumption monitors of 800,000 cars registered in Europe from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, up from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are decreasing,” said a lead researcher participating in the study. “This gap is widening and poses a serious issue. As a result, PHEVs pollute almost as heavily as petrol vehicles.”

Key Factors Driving the Discrepancy

Researchers attributed most of the difference to inflated estimates of the “utility factor” – the percentage of miles driven in electric power relative to total mileage. They determined that just 27% of driving was completed in electric mode, whereas official assumptions assumed 84%.

Additionally, when operating in EV mode, pollution amounts were significantly higher than official estimates. This occurred because electric motors were not strong sufficient to operate independently, resulting to combustion motors using gasoline for nearly a third of the distance completed in EV mode.

Regulatory and Economic Consequences

Based on estimates, the underestimation of PHEV emissions enabled four major carmaker groups to avoid more than €5bn in fines from 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ targets.

Additionally, owners of PHEVs would pay about €500 extra per year in running costs than is assumed under laboratory tests.

“The bold claims that automakers like to make about their plug-in hybrid vehicles are obviously way off the mark,” commented a automotive expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are helping the environment and saving money. In reality, PHEVs are little improved than regular petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and running expenses.”

Policy Debate and Automotive Pressure

Hybrid cars have recently been brought again into political debates as automakers have pressed the EU to relax CO₂ targets. A planned ban on sales of new internal combustion cars in 2035 has faced heavy pressure from the automotive sector and opposition from EU countries with large automotive industries.

Some high-level politicians have suggested plug-in hybrids as a potential “compromise” option to introduce in the legislation.

An external energy economics specialist, who was unaffiliated with the research, described the report a “very useful contribution” after years in which parts of the car sector argued there was too little data to accurately assess real-world emissions.

“The results demonstrate, beyond any doubt, that the difference between official and actual PHEV fuel consumption and CO₂ emissions is significantly greater than for gasoline or diesel vehicles,” they stated. “Any policy adjustments regarding PHEVs should be implemented with extreme caution and in the light of this data.”