Every unit will have at least 1 battery bank available to them. This will be the primary source of electricity which does a couple of things. However, the bank will likely be located in the basement as there will likely be no room to place the bank in the apartment. The solar panels will fill the banks up, and send the rest to the grid for any usage in the future. The advantage of using a battery bank for the source of power is to allow for conditioned electricity. This means there will be no electrical surges or spikes. This will help protect your devices even though you have a whole unit surge protection at the electric panel located in the communications closet. The second reason that electricity is provided by the battery bank is no delays in power outages. A power outage might take a second or two for the battery bank to take over. This could damage a computer, especially during an OS update. You would be stuck taking it into the manufacturer or an authorized repair center to get the OS reinstalled, and updated. This will mean that if you do not have a backup, you would lose all of your data all because the battery bank was not the primary source of electricity.