Steve,
One has choices, they can direct grid-tie, sans battery, and use the grid as a 'battery'. Or, they can be completely off grid and need a lot of storage. A third option is what I am choosing, I will grid tie and use a small battery bank so I can have refrigerator, freezer and lighting if the power goes out and still be able to use the "Grid" for "storage" and lower my electrical bills, not my electrical costs. I will also be able to use any single phase 120V tools or appliances within the limits of my system as long as the sun shines.
IF one chooses to pure grid tie, when the grid goes down, one has no backup power. The PV array will still be producing, but without the inverters getting a signal from the grid one is shut down. With a small battery bank, and a different style inverter, one can have as much 'backup' as they wish to afford, I will choose enough to easily power my refrigerator and freezer, a bit of lighting, internet and fans.
Eventually, I do plan on an off-grid home. It will require a larger battery bank. It will also have a large wind turbine (by stand-alone, hobby style units) and I will probably use water chilling to store some of the needed energy in this area. The outlay for a true stand alone system will be substantially more. The freedom and attitude will be priceless.
Ron