Plug-in hybrids have enjoyed a surge in popularity but a study published Thursday showed they are polluting far more than most buyers think, as they run on batteries less than regulators expected.
The study by the International Council on Clean Transportation (ICCT), a lobbying group, looked at data from the onboard monitors of roughly 920,000 plug-in hybrids registered between 2021 and 2023. It found a “substantial and fast-growing gap between real-world and type-approval CO2 emissions for PHEVs registered in 2021–2023.”
The type-approval norms include an assumption by regulators about the pollution the vehicles would emit based on the distances they would be driving using the battery and the distances using internal combustion engines. But the study found that average CO2 emissions in real-world driving were 3.5 times higher than the 2021 type-approval values, and 4.6 times higher than the 2023 type-approval values.
The growing difference was due to an assumption that bigger batteries would lead to increased driving on battery power, but the real-world use data did not bear this out.
