Grid-tied solar works seamlessly and invisibly with utility power. The basis of operation is simple. Whenever the sun is shining the solar modules generate electricity. Power flows from the PV system to the nearest point of use – anything that’s running in your home. Any excess flows from the home out into the utility’s wires to your neighbors, spinning your meter backward in the process. At night or during cloudy periods, utility power runs all of the loads in your home. A basic grid-tied PV system only has five components: PV modules, mounting, safety disconnect protection, an interactive inverter, and in PNM territory, a second meter. In most cases, the output of the system connects to the same breaker panel in your home that is served by utility power. The system is simple, efficient, reliable, and maintenance-free.

Here are simple block diagrams showing how energy flows in each approach. First is a diagram of normal utility power with no solar in the mix:

Next is a diagram of a grid-tied system on a home (or business) with utility power:

Finally, here is a diagram of a PV system for an off-grid home:

An off-grid system is completely different. The power from the PV array charges batteries, controlled by a charge controller. The batteries store power for use at night and during cloudy periods. The batteries feed an independent inverter, which creates AC power similar to utility power and also serves as a backup battery charger from an external source such as a generator. A system monitor tells you how the system is performing.