Appears to be a type of energy storage unit which could be or maybe not be attached to solar PV systems. Imagine that your house can withstand a power outage of a few hours using a set of Li-Ion batteries or perhaps endure charging daily in an off-grid arrangement?
The price of such systems has been unduly high over the years and even with really good deep discharge lead-based batteries, they couldn't be discharged much below 50%. Some Li-Ion battery chemistries allow thousands of far-deeper discharges - using 80% or more of their state of charge. I do believe that in Japan, they have been delivering such "Home UPS" systems over the years and many wealthier families in India use these due to the constant power outages.
With the right Li-Ion charge controller (I hope PWER builds this using their own engineering) you can have a battery management system that goes beyond the charge controllers on the market today. The only thing holding something like this back is price. A whole home generator isn't that expensive. This kind of battery system must be cost effective.
BTW - Panasonic makes the battery cells for many laptops and also the Tesla Model-S EV. They have very high energy storage per Kilogram. I would rather see a LiFEPO4 chemistry (LFP) used for home battery storage due to them being less prone to issues with overcharging dangers. The Battery Management System (BMS) must guard against any one cell being overcharged. And that means a little more complex wiring and circuitry.
Also, in Japan, they want to smooth out their grid a bit due to the shutting down of Nuclear facilities. Google up this story: On September 11, 2012, Panasonic announced its plans to begin the full-scale development of its Smart Home Energy Management System (SMARTHEMSTM*1) business in Japan from October 21, 2012 - where it goes into more details.
Next up in the industry will be the use of Electric Cars (Leaf, Volt, Tesla) as standby power for homes using an export module from the cars' batteries. I suspect Nissan will lead the way with this measure. Still more costly than the standby generator but some people will help kick start the industry. Us "Power Hungry" Americans tend to use a lot more power than that used in foreign countries, so these solutions really are more fitting to non-USA and Canadian homes or perhaps the new rising trend of "tiny homes", those little 60-100 sq. ft. homes that our grandchildren will be living in after the economy grinds to a halt someday :)