An energy-efficient dehumidifier reduces the moisture content in the air with minimum energy usage. The efficiency of any dehumidifier is measured by the quantity of water (in liter/pints) that it can remove from the air indoors per kilowatt-hour.
Humidity is present in most houses due to the air that circulates within from outside. Leakage of air from gaps around floors, ceilings, doors, windows easily allows humid air to enter. Basements of houses are usually cooler and can cause condensation of water from the humidity in the air. Water seepage and formation of water vapor from activities like cooking, drying clothes can also add to the humidity of an average home by around 80 liters, i.e. 20 gallons a day.
The moisture in the air is removed by the dehumidifier through its compressor, fan and condenser coil. In simple words, it acts as a refrigerator, except that its main function is to remove water from the humid air instead of cooling it. A dehumidifier continues to work until its tank is full or the moisture in the air reaches a preset low threshold. Automatic drainage of the water collected into a floor level drain ensures that the dehumidifier does not need constant attention. Another alternative is to have a visual indicator that switches on when the water tank is full.