When I had solar panels installed, I had the battery installed with it. It's nowhere near enough to run the whole house, so I segmented 8 circuits in the house to switch to battery when the power goes out. It's been a little over 3 years, and the power has only gone out a few times. The last time was after Hurricane Sally. The battery worked as it should have. I had television, Internet, telephone service, lights, refrigerators, etc... All good, but no AC.
Having said that, If I had to do it over, I'd get a whole home generator installed for much less than the battery. The Chemlite battery cost me 9,500 dollars. Just for the battery - not including the cost for installation. A whole home generator would power the AC system as well as my water pump. In order to do that with batteries, I'd need to add quite a bit of capacity. I'm not sure even then that the batteries would be able to handle the loads of either my AC system or even the water pump. The demand of those 2 systems might damage the batteries.
I'm sure in years to come, battery technology will improve to the point that a whole home backup system will make sense, but right now, coming from a person with a bit of experience, I'd advise anyone to look at a generator rather than a battery system.
Also, I installed a solar system - a single 100w panel, a charge controller, inverter and a 100 wH deep cycle batter in my shed for power out there. I power a couple of lights in the shed, one outside motion sensor light, and have 2 receptacles installed. I'm sold on solar and on batteries, but not for a whole home situation.
It was kind of nice having the battery though. I believe the power was out for 4 days or so after Sally. The neighbors brought me their phones and gadgets for re-charging. In return, they filled my 5 gallon buckets with water. They're on city water. For some reason, the city didn't run the line down the road to a few houses down here so we're on well water. Free water is nice, but when the power goes out, the well pump goes out. Not good.
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