PV Panels
On sunny days the photovoltaic panels convert sunlight to direct current (DC) electricity which can be used to charge batteries or to supply loads.

Charge Controller
The charge controller manages the efficient charging of the batteries using the DC energy from the PV panels.

Batteries
DC energy is stored in deep cycle lead-acid batteries, which give back the electricity as needed, especially when no charging energy is being produced. Like a bank account, energy put into batteries over a period of time can be taken out more quickly when needed. Like a bank account, you cannot take out more than you put in. Moreover, lead-acid batteries need to be quickly 100% re-charged to remain in good condition. To maintain a good lifespan, they should not be drawn down below 50% charge.
In more detail: Battery life can be estimated by average depth of discharge and by time to full recharge. A battery with an average of 30% depth of discharge will last about 1,200 discharge/charge cycles, or about 62% longer than the 450 cycles at 50% average depth of discharge. A battery with an average of 50% depth of discharge will last twice as long or more than if it uses the maximum 80% average depth of discharge.

Inverter
The inverter converts the DC energy from the batteries or panels to 120 volts AC for standard house loads.

Generator
A generator can be fueled by diesel, propane gas, or gasoline. It is another source of AC power for heavier loads and a backup for charging the batteries when there is insufficient sunlight.