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The trick is getting everything to work together. Typical solar (without battery) installations actually work *with* the grid. If you generate more power than you need, the balance goes to the utility and you get *some* money for it. This is *net metering*.

The problem is that it is grid-tied - if the power goes out then you very likely have no power at all. That's because the system is designed to synchronize with utility power. No utility power and it doesn't know what to do and shuts off. If it stayed on, the power would be going out and zap utility workers. (The same problem happens if you use a generator and don't cut off the utility connection, which is why you need a *generator interlock* or a transfer switch if you connect a generator to your breaker panel.)

Battery backup solves the problem because it is designed to charge when utility power is on and discharge when utility power is off. If you use solar (off-grid) then it charges when solar is on and discharges when solar is off (night). But getting enough battery backup to power *peak* loads is not easy or cheap. Plus your battery backup is typically designed for a day or so of power. Power outages can last longer than that, so there is a natural inclination to pair them with some additional power source, which can include solar, generator (but then you are paying for a generator that is only used in *some* outages) or the latest is vehicle-to-grid if you have an EV that can do that.

So utility power + battery backup + solar is a very natural pairing. It is quite different from a totally off-grid battery + solar setup as then the batteries are cycling frequently (every night) and you size your system based on peak loads.

With utility + battery + solar, you size based on *necessary* loads and manage accordingly during an outage, just as you would with a small (not whole-house) generator. Which is not a big deal - refrigerator, computers, lights are all small loads. With a reasonably sized backup you can also run HVAC (except electric resistance heat, but hopefully you don't have that), some cooking appliances, even the clothes dryer - you just might need to turn off one large appliance before you turn on another. The great thing is that if you have solar and manage well, you could do just fine for an extended blackout as long as the sun still shines for several hours each day and you manage your power well. If the power goes out the day before Thanksgiving, you may have to skip the turkey (ovens use a *lot* of power), but at least you can leave it in the freezer and know you have enough power to keep it running.

The bottom line is in the control electronics. This sits between solar, battery and utility to manage everything. There is no fundamental reason you can't have a system which handles it all, includes a large battery pack, and does *not* require solar. However, a company that sells packages based primarily on solar panels may not be interested in selling you that equipment. You can't just "roll your own" - for safety reasons it all has to be done right to avoid backfeeding the utility grid, and if you want to add solar in the future the utility will likely have rules as to certain key specifications of the system that you will need to plan for at the beginning to avoid extra costs.