Some random googling for "average daily electric usage" seems to indicate that Americans use about 20-30 kWh per day. So a 10 kWh battery will only over 1/2 to a 1/3 of day. As a power backup this seems pretty flimsy. People would have to buy 2 or 3 of these for a single day power backup, which seems a little crazy. Maybe in combination with solar/wind? I dunno, a generator seems more practical, you can just go buy more gas for it.
Maybe if my applianced knew when they are running on battery power and could auto adjust their consumption. Otherwise, I am just going to find out about a major power outage a few hours after everyone else.
Using it for cheeper electricity is a little funny too. Currently, electricity is already cheep. Even if it cut my electricity bill in half, its not really all that much per month. It's like cutting my bathroom tissue costs in half, not really going to make me a rich man.