Keeps water from freezing in winter thermostatically controlled to operate only when necessary. Plug cord into outlet or extension cord during winter months. Operates automatically. Unplug cord during warm weather. 20 watts of power thermostatically controlled holds 32 ounces easily fills from top mounts on outside of cage. Size is 20 Watt. Dimensions are 4.25 X 4.5 X 11.5 UPC Code = 085045000208