Solar power cost effective calculation?

Yes I think you may have done something wrong. The company that installed my solar panels helped us figure it out and in the end we realized it really would be worth it. We decided to take the plunge and do it and now 6 years later, we realize how much money we are saving ourselves. Also a good company should be able to get you some good rebates, which really helps a lot. I think you should look into it further. Good Luck!