Have you considered an Antminer L3+ instead? (for mining Litecoin and Dogecoin with merged mining), they're cheaper, consume much less than Bitcoin ones, and two of these generate more than an S9.
Why Mine Litecoin Solo?
Do you want to get a $500 reward?
If you mine Bitcoin solo, you can earn at least several hundred thousand dollars. The chance of this happening is very, very small, but what miner does not hope for luck.