Electronic air cleaners for use in heating, air-conditioning, and ventilation (HVAC) systems and associated methods and systems are disclosed herein. In one embodiment, an electronic air cleaner (100, 200, 300) includes one or more collecting electrodes (122, 322) having a collection material with a porous, open-cell structure and a conductive internal portion (125, 325). The collection material can be configured to collect and receive charged particulate matter in an airflow path. After a period of time, used collection material can be removed from individual collecting electrodes (122, 322) and replaced with new collection material.