The answer to 'when to replace dehumidifier' is that you should typically replace your dehumidifier every 5-10 years, depending on how often you use it. Dehumidifiers have a limited lifespan and their efficiency and performance will decline over time, especially if they are used frequently or in harsh environments.
Over time, the internal components of a dehumidifier can wear out, the refrigerant can leak, and the unit may become less effective at removing moisture from the air. Replacing an old, inefficient dehumidifier can improve the air quality in your home and save you money on your energy bills.