When I was installing it on my house it costed me exactly 0$. Essentially the solar panel company rented my roof space installed panels there and sold me electricity. The cost of electricity was even cheaper for me, since there were no delivery charges.
Alternatively - take credit. While I have not done these calculations, it is plausible that you get even or even benefit from installing solar panels while taking credit (this would work better few years ago, when the rates were low)