Current energy storage technology is lacking, so on the "good" days you have surplus capacity and nowhere to go with it. If you are grid tied it depends on many factors specifically how much the end user is being compensated for the power contributed to the grid. When you consume grid power you pay retail, when you supply you get wholesale pricing, unless that is different in your area. Any one that invests 5 digits into a solar power system on the premise of a 10 year ROI is nuts..... especially in Indiana. If you have plenty of cheap land in the dessert and grid tie it might be viable at some point.