The solar panels sold at SunRotor may be slightly different in wattage than the currently listed item. This is because we are constantly looking for more efficient and cost-effective options as technology changes. We currently keep two types of panels, a 60-Cell PV Panel usually in the 300-325W range, and a larger 72-Cell panel with 330-355W output. The smaller 60-Cell options have a lower voltage, which allows systems pumping at a low TDH to operate smoothly at the intended voltage. This helps to increase the life of the pump, as it's not being overdriven on a much lower load. The larger 72-Cell option has both higher voltage and output, which ensures higher TDH systems have enough power for full operation.