The Hunter ET System is an easy-to-add accessory for Hunter Pro-C and PCC controllers. Using highly advanced technology, Hunter ET measures key climatic conditions to calculate local evapotranspiration (ET) factors. ET is the combination of two separate processes whereby water is lost from the soil surface by evaporation and from the plant by transpiration. The ET System will initiate a new schedule to replenish only the water that is actually needed for plant and soil conditions. The Hunter WiltGard™ technology can intervene to trigger protective watering when extreme conditions threaten vegetation. The result is a dramatic savings in water, healthier root zones, and longer plant life.