Solar Roof Calculator We invite you to use this solar roof price tool to generate an estimate for your solar roof project. The tool is intended to provide a rough estimate of cost. Your final quote will vary. Inputs Usable Roof Size (estimated in Square Feet) Average roof sizes range from a usable size of 2000 to 4500 square feet : Average Monthly Power Bill : Number of Expected Powerwall Units : Solar Roof Estimate Estimated Powerwalls: Estimated Tesla PV Roof Cost: Estimated Powerwall Cost: Estimated Other Cost: Estimated Total Cost: Federal Tax Credit: Cost After Tax Credit: Schedule an Estimate Today`