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U.S. Department of Energy Energy Efficiency and Renewable Energy

Equipment Required for Stand-Alone Systems

In addition to purchasing photovoltaic panels, a wind turbine, or a small hydropower system, you will need to invest in some additional equipment (called "balance-of-system") to condition and safely transmit the electricity to the load that will use it.

A diagram of a typical, alternating-current, battery-based system. It shows the wiring/current traveling from a photovoltaic module (a square-shaped box containing several circular solar cells), connected to a grounding circuit, to a charge controller (a rectangular-shaped box with a knob on the left and two display windows with gauges on its front). From the charge controller, the current/wiring then travels to an inverter (a rectangular-shaped box with two electric outlets) and a battery (a rectangular-shaped box with two knobs on top), both of which are connected to another grounding circuit. A portable, box-shaped fan, called the electric load, is plugged into one of the inverter's electric outlets.

Diagram of a typical AC, battery-based system.

Download high-resolution diagram:
JPG (ZIP 25 KB) | EPS (ZIP 252 KB)

The amount of equipment you will need to buy depends on what you want your system to do. In the simplest systems, the current generated by, for example, your wind turbine is connected directly to the load. However, if you want to store power for use when your turbine isn't producing electricity, you will want to purchase batteries and a charge controller. Depending on your needs, balance-of-system equipment could account for half of your total system costs. Your system supplier will be able to tell you exactly what equipment you will need for your situation.

Learn about the major balance-of-system equipment for a stand-alone system:

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