Tesla Battery

At a few cents 'profit' per kilowatt hour, how long will it take to pay off the initial investment?

In looking at the Yahoo article, "According to Chowdry, a 10kWh battery could cost $13,000 with a 50% rebate from PG&E."

So this would suggest the battery would cost $26k 'retail' without subsidies from all the other ratepayers.

Then "The buyer who talked to the analyst purchased his unit for $1,500 down, followed by 120 monthly installments (10 years) of $15 each."

$1,500 + 120 * $15 = $3,300 which is very different from $13,000 or $26,000.

So, I'm confused.

" . . . . with the interviewed user saying he's making between $10 to $12 each month from the extra energy his unit produces."

But we're not sure if that $10 to $12 is before or after he pays the $15 monthly installments. The other linked article says $12 to $15 so there may have been a copy error from BGR to Yahoo.

Just doesn't seem like a good deal unless perhaps you can get a huge differential in the peak to off-peak rates. I can only see this Musk battery being useful for off-grid applications, but then again for stationary applications, large format wet-cell lead-acid batteries are likely to be much cheaper and safer.

Maybe they mean a 50% rebate on the 13k, but that still leaves a shortfall. Pricing of Li-ion batteries must fall with a quadrupling of manufacturing capacity over the next couple of years. Does this mean that

1. Tesla are moving out car manufacturing as it's primary business. Acknowledging that it is a small scale automotive manufacturer but can be a large scale battery manufacturer?

2. That the expected price point in the 2 years for the 10kWh set will be around the $6.5k?

It bothers me that some things are feasible only because there is a government subsidy. Somebody is paying the true cost (or will be, when the "elephant in the room" national debt is addressed).

How many years warranty is given on this battery,what is the type(plate/electrolyte), how much will be the mainteance cost,who will undertake maintenance,how to dispose the used electrolyte?.