Spending tens of thousands of dollars on batteries that only last a few hours when grid-power is lost is not a luxury the typical person can afford. But solar panels that are cheaper (and provide revenue through net-metering) will revolutionize the energy industry.
The average homeowner uses 30 kW-hrs of electricity a day. So... what, three Power-Walls per day of backup energy for $10k + installation costs + inverter costs? With a power output of only 2kW? This is going to cost maybe 20k or 30k for a solution that gives you power for more than a day.
In contrast, a simple gasoline generator will get you 5kW of power (6kW peak) and run for as long as you have gasoline. This crazy solution costs like $600 from Home Depo... and has several decades of experience to prove its effectiveness.
http://www.homedepot.com/p/Powermate-5-000-Watt-Gasoline-Pow...
Generator + Solar Panels is still looking a hell of a lot more practical than Solar Panels + Battery. $50 of gasoline is going to run you ~25 gallons, enough to last 2+ days without any power. And if a crazy hurricane "Sandy" situation occurs again, you can always go out to the local gas station to grab more gasoline for day 8, day 9, or day 11 without power.
I mean, seriously? 10kWh per PowerWall is laughably small.
----------
I mean, when do you lose power for extended periods of time? Answer: when major hurricanes or snowstorms hit. That's what. It isn't like your Solar Panels will work while they're completely covered in snow. You'll need the generator if you actually want reliable off-grid energy anyway.