Batteries afford the local solar power generation system the ability to store power and use it when required. Since electricity moves at the speed of light, this isn't just a good idea, it's the law. Batteries are the only thing on the planet that can store electricity without relying on gravity. Batteries are able to take power from a source, and then power a load later. Think of them as a power tank. As long as you buy high quality "FLOODED" or "AGM" deep cycle batteries you should be able to charge them rather quickly, and discharge them quickly too. The more you do, the faster they burn up, but nothing lasts forever. The reason you put up with batteries at all are the design changes, and reconfigurations your can make both later, and on the fly. Here are a few examples of the benefits of batteries in your solar installation.
Reduce total amps to the utility.
For instance, a bank of batteries would be able to catch solar power far faster than a small inverter could push it into the grid. Or batteries could arrest the high amperage load characteristics of your machinery.
Since the utility company sees max amps over the period, and total consumption, using both to compute your bill, often situations arise where you would like to control max amp load. Batteries can help you remove the consumption amperage peaks that affect your bill.
Avoid Costly Upgrades.
Again, total amps the utility feeds or takes are the article of discussion. When your home or business needs more power, for a hot tub, computer room, etc. you are often faced with upgrading the panel itself. Sometimes the breaker box itself is not adequate and equipment is necessary outside of your property to provide the service requested. Batteries can emulate the higher current and voltage requirements of your business for a short time without adjusting the utility grid behind them.
Meet Local Utility Regulations.
This is the theory behind adding multiple solar arrays behind one tiny inverter. The solar power generated in 6-8 hours is caught by the batteries, and then fed to the inverter over 24 hours to push the loads, and feed the grid as the utility will allow. The following day, the solar panels refill the batteries, which again feed back into the grid as regulations allow (regulated by the software). This allows the electricity customer to use their systems at full tilt, all the time (75 amps continuous in a 100 amp utility service) for instance, producing as much power as fundamentally possible when weather permits.
Allows for a generator - NO MORE LOST FREEZER FOOD!
A generator takes time to start up, normalize, and then begin feeding power to loads. This process can take as little as a few seconds, up to 30 minutes. During this start up time, systems without batteries experience no power whatsoever. Batteries provide the power in this interim situation, keeping the clocks throughout the house correct. Basically, this setup protects every computer, big screen tv, and refrigerator as if it were connected to a little battery backup. This is how data centers, government buildings, hospitals, etc are designed to operate in a failure too. Now your freezer will keep the food during the next 10 day power outage.