The innovative car company, Tesla, is now offering to run your house on a battery.  The new  power wall has two sizes:  in 10kWh and 7 kWh daily cycle models, which could run 4 to 3 homes on the road system, respectively.  What is very nice about these batteries is the ability to tie additional ones together so that you can have an aggregate source of  90 kWh (for 10 kWh batteries) and 63 kWh (for 7 kWh batteries).  With plants being built for this scale of lithium-ion battery technology,  this is an answer to on demand electricity when outages occur, or if you are off grid. Take a sneak peak:
Now, if you add solar to the equation, these Tesla cells open up a whole new world for those who are not hooked to the grid.  (Tesla is now working with  SolarCity, and has attracted enough customers to equate to a sixth of Alaska’s population so that this partnership takes up almost half of the household battery storage market).  For some time in solar has been readily available from the view point of converting radiant heat into electrons, but often it has not been cost feasible due to 1) the cost of the silicon PV panels and 2) storage of the electrons.  With PV panels down to almost a dollar a watt (where at the beginning of the century they generally were over ten dollars a watt) the conversion is cheaper than ever and with the lithium ion batteries the storage is now reasonable for many residences.
 Yet even with charging the batteries off the grid, the ability  to store excess energy during the middle of the night when there is low demand and then burn up the KW during peak hours (generally a higher cost rate for KW) has helped some people to save money due to taking advantage of daily rate differentials.  One  project is using 10-killowatt-hour batteries to gather 2 days of power and have it on hand.  This is a great advantage when planning for emergency/disaster power outages.  Suppose wind and ice storms that have become more frequent in the fall the last several years take down your toyo stove and refrigerator….This may not be a big deal if it is just for a couple of hours, but depending what time of year it is you could have a real problem on your hands if you are talking two days.  Broken pipes, food going bad, cost of a motel, etc…  And though you can use a $500 generator for a couple hours of outage, does everyone in your home know how to pull start it or push button start it in cold weather?  Though more expensive, possibly a super cell battery would be of better use…