How Many Solar Panels Do I Need to Power My Home? 1200Kw p/yr. He estimates 375 sq ft. or 63 100 watt panels. That would take 420 15 watt panels selling for $65 at harbor frieght (1'x3')=$27,300 (abt 1300 sq ft) plus regulators, controllers, connectors, batteries, etc. Harbor fright's panels might not be the best choice. But it was where I knew I could look and get a direct price on panels.