The cost and size of PV systems batteries bank depends on the type, capacity (ampere-hours), the climatic conditions in which it will operate, how frequently it will receive maintenance, and the types of chemicals it uses to store and release electricity. A PV system may have to be sized to store a sufficient amount of power in the batteries to meet power demand during days of cloudy weather. This is known as "days of autonomy."

Most types of batteries contain toxic materials that may pose serious health and safety problems. The Public health regulations, battery companies, and PV system designers recommend that lead-acid and wet cell batteries, which give off explosive hydrogen gas when recharging, be located in a well-ventilated space isolated from the other electrical components of the system and away from living spaces. Allow enough space for easy access during maintenance, repair, and replacement. Most important, maintain the battery according to the manufacturer's instructions, and recycle the batteries properly when they wear out.