There's no need to connect only the A/C to solar, nor is there a need to use batteries. Both of those problems are solved with grid-tied solar. The solar electricity system works alongside your regular, and the A/C just plugs in normally. You never need to worry about switching. During the day, if the A/C is drawing power, the solar goes into that, reducing your draw from the electric company. If the solar generates more than the A/C needs, the meter is driven backwards. At night, the meter runs forward again. For example, the meter may read 5000 in the morning. By evening, maybe it reads 4975. At night, it creeps back up to 5005. When the meter reader comes, you would be billed for only 5 kWh. That's the general idea. Also, consider whether you can insulate your home more, and whether you might want to change out your air conditioners for new, DC inverter mini-split units. Those can use a fraction of the electricity per BTU of regular air conditioners.