A quick look didn't show price/capacity of the batteries. I...

A quick look didn't show price/capacity of the batteries.

I calculated that a Tesla powerwall would need 20 years and about 7,000 deep cycles to repay it's capital cost if charged by domestic solar where there is a 6c FIT anyway. That may be as many as they can do.

Like the Tesla S these batteries will be the plaything of rich early adopters. The masses will need to see a X10 improvement in the cost/capacity ratio before they become common place. Not as easy to do on what is in reality a commodity [battery] as it is with technology [memory storage]. It is too easy to think that technology will drop the price of batteries 20 - 30% each year. Didn't happen with lead/acid batteries. They went up every year.