With a full PB install, large systems are returning a 2:1 payback with 1st cell savings near $3k these days. So much so, you could pay a CC with interest, whatever you were spending monthly and still make out in the end.Maybe a no-interest credit card will help spread out the costs?
If you can DIY the 1st cell, or future cells that anyone can DIY in 10 mins, the payback nears 4:1.