What is the payback period on a $25,000 solar system?
With the default 30 percent incentive, a $25,000 system has a net cost of $17,500. If your monthly bill is $200 and the array offsets 90 percent, annual savings are about $2,160, giving a simple payback of roughly 8.1 years. The calculator divides net cost by annual savings, so lower bills or smaller offsets stretch the payback longer.