The SunRotor SR-4 Solar Submersible Pump is one of the most cost-effective options currently offered on the marketplace. Used primarily for livestock watering needs, this pump has replaced many failed windmills throughout the country. With a single 325W solar panel, this product can pump the full 4 gpm at a depth of 150 feet. With the controller, it features low-well sensor, timer reset, speed control and tank-float options.