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The intent of this report is to help qualified individuals maintain and inspect PV systems safely. Qualification to conduct such inspections is earned by direct on-the-job training under qualified supervision or through training programs offered by accredited educational institutions or manufacturers. It should be noted that many testing and maintenance activities require two people to be performed safely and efficiently. Currently, an employee who is being trained for a task, demonstrates the ability to perform duties related to that task safely, and is under the direct supervision of a qualified person is usually considered to be a qualified person. As the number of U.S. PV installations grows, the industry will increasingly focus on O&M. PV systems have multi-decade lifetimes, and regular O&M helps optimize an installation’s ROI over its life. There are currently three working groups focused on this issue, and they will develop a more comprehensive O&M approach in the next few years. In the meantime, this report serves as an introduction to O&M for PV installations. The conclusions of this introductory report include: To maintain quality control and safety standards, it is important that only qualified personnel work on PV installations. It is not always easy, however, to identify qualified personnel. The authors suggest skill and knowledge guidelines for PV technicians in the Qualified Personnel section of the INTRODUCTION chapter; Safety is a serious concern when servicing PV installations. Early PV systems often had maximum system voltages less than 50 Vdc, but 600 Vdc systems are now common, and 1,000 Vdc systems are allowed by code in commercial and large-scale installations. Safety considerations require that qualified personnel use properly rated equipment and be trained for servicing the higher voltage systems; Qualified personnel should always work in teams of two people when working on live equipment. In addition, on a given jobsite, there should always be at least two qualified persons trained in CPR; Not all installations have appropriate signage, and qualified persons must be trained to recognize potential hazards with or without signage present; System uptime and availability is a key objective of O&M. Inverters that are offline can have a dramatic negative impact on the ROI of a PV system. Inverter failure rates are important to ROI, but even more important than how often an inverter goes offline is how quickly it can be placed back into service; Low power production also impacts ROI, and O&M personnel need effective strategies for identifying and correcting problems quickly. One specific recommendation is to stock critical parts that have long supply lead times.