Next on our list is the stand-alone system. The image below is a schematic of a stand-alone solar electric system. As you can see, it is very similar to the grid-connected system with battery backup. You will notice two distinct differences, however.

First, there is no connection to the grid. Thus, no power is shunted to the utility grid. This system, which must have batteries, “stands alone.”

Second, this system usually includes a backup generator. It can be run to charge the batteries when they run low. Some people install wind turbines to serve as a second charging source, according to Johnny Weiss, Director of Solar Energy International.

As illustrated above, the main power source of a stand-alone system is the PV (Photovoltaic) array. Electricity flowing from the array into the house first travels to the charge controller, then to the batteries. When electricity is needed in a home or office, it is drawn from the batteries. DC flows from the batteries to the inverter. The inverter converts the low voltage DC solar electricity to high-voltage AC current. It is then delivered to open (active) circuits in the house via the main service panel.

Stand-Alone Solar Array

If the batteries are full, the system merely shuts down temporarily so the batteries don’t overcharge and fry. This task is managed by the charge controller with its high-voltage disconnect.

Stand-alone systems shunt additional power into the batteries during daylight hours for use at night. But batteries can also be called into duty during the day, for example, when clouds block the sun.

Like other solar electric systems, stand-alone systems require a couple of disconnects, to enable you or a repairman to service your system without being electrocuted.

Learn more about Powering Your Home with Solar Electricity .