Found something interesting: I was looking into the option from...

Found something interesting:
I was looking into the option from Sonnen batteries; it is not my intention to promote this, just mentioning what I found:
They have campaign to provide batteries on a flat fee (this is my understanding) for people who already have solar system installed and they will have the control of the battery to take advantage of the electricity wholesale market; the  customer will have a flat fee with a yearly quota of free electricity. (this is how I understand it; might not be right, so feel free to correct me)

Sounds great and I said this is a way to go; I would wait for Tesla to provide something similar with the Power Wall with a bit bigger batteries; this is already (partially) available in SA.
I've checked the site for Sonnen this morning again and this is what I found:
"The server is temporarily unable to service your request due to the site owner reaching bandwidth limit."
I think the interest in storage batteries is much higher than anyone expected.