Calculate your solar array size.
Estimate your cost per Watt installed.
Hint: If solar is popular in your state (CA, CO, NJ) and you have asphalt or composite shingles, then use $4-$6/W. If solar is less popular in your state (VA, TX, MI) and you have a tile roof, then use $6-$8/W. If you’re unsure, $5.5/W is about the National average.
This calculator assumes no State or Utility rebate. Go to www.dsireusa.org to see if your area offers solar incentives. If it does, subtract it first from the Estimated System Cost. This is your total cost of installation.
Then calculate the Fed Tax credit by multiplying the result by 30% (0.3). Lastly subtract the Tax credit from the cost of installation to get your Total Cost after all incentives!