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

Tribal Energy Program

Designing a Photovoltaic System

To design a photovoltaic (PV) solar power system, it is important to estimate or measure the load and to obtain the best solar resource data available.

An excellent place to start is PVWATTS, a Web-based performance calculator for grid-connected photovoltaic systems that can be used for locations throughout the United States. This calculator was developed to permit non-experts to quickly obtain performance estimates for grid-connected photovoltaic systems.

One of the tools used within this calculator is a Solar Atlas data map. The Solar Atlas data map allows the user to select a region of interest in order to calculate the solar resource potential for that area. PVWATTS also allows the user to input user-specified PV system and cost of electricity data. The output is monthly energy production and value from the PV system for the specified region.

PV design tools are available to assist in sizing and configuring the system; choosing between on-grid and off-grid configurations; estimating the power output; analyzing the building energy needs; modeling shading, temperature, and thermal performance; performing an economic analysis; calculating emissions benefits, estimating seasonal weather impacts, and comparing the available PV modules. Typical software tools include PVSYST, PV DESIGN PRO, WATSUN PV, PV CAD, PV FORM, BLCC, HOMER, ENERGY-10, and AWNSHADE. Some tools are available for free but most require a user feel.

Information about these and other design tools are available on the following Web sites: