Definitely would look into all the rebates and also what your rate your power company will pay you for the power you produce. Some companies do a 1:1 swap but DTE in Michigan I believe pays 1/4:1 so you they buy it from you for a 25 cents and sell it to your neighbor for a dollar. But Chris is correct that the solar companies can run a simulator to get an pretty accurate idea of your production. I used to work for a large solar company and they use data from local airports for cloud and weather data along with GPS and the travel of the sun through the yearr to predict how much sun will land on your roof. Then they determine how many panels you will need to get the production you want. The power company may limit the amount of solar you can install as well possibly not allowing you to produce as much or more than you use. One other benefit is that batteries also qualify for the rebate and provide some power during a outage although they are expensive.
