Aprilaire 700 Automatic Humidifier Has an evaporation capacity of 0.75 gallons per houramong the highest capacity humidifiers sold Humidifies tightly constructed homes up to 4,200 square foot in size Features truly automatic control Delivers optimum levels of humidity control with the Automatic Digital Humidifier Control. You never have to monitor your settings or wait until you feel uncomfortable Provides vital service, temperature and relative humidity indicators in manual mode as well Performs quietly with simple annual maintenance