AE 868
Commercial Solar Electric Systems

Operation and Maintenance (O&M)


Maximizing the performance of any PV system is one of the priorities of owners and integrators. This can be done with routine maintenance to ensure optimal operation conditions. Since PV systems can be owned by individuals, organizations, or utilities, there must be a set of practical guidelines to operate and maintain these systems to minimize downtimes and maximize the return on investment. The maintenance requirements vary depending on the system size, installation type, and locations. For example, stand-alone systems require more maintenance consideration due to the addition of batteries. Furthermore, manufacturers may provide maintenance guidance or procedure for components.

Maintenance Approaches

There are several major O&M approaches that exist in the market today, and each comes with tradeoffs. In simple words, each approach aims to achieve the three key goals of an effective O&M:

  1. Reduce costs
  2. Improve availability
  3. Increase productivity

There are three main strategies for maintenance: Preventative Maintenance, Corrective or Reactive Maintenance, and Condition-based Maintenance.

Preventive Maintenance (PM)

This strategy includes routine inspection and servicing of equipment to prevent breakdowns and unnecessary production losses. PM strategies can lower the probability of unplanned PV system downtime. However, the upfront costs associated with PM programs are moderate and requires more labor time, and the increased inspection and maintenance activity contribute to site wear and tear and perversely expedite system malfunctions.

Corrective or reactive maintenance

This strategy addresses equipment breakdowns after their occurrence to mitigate unplanned downtime. This strategy allows for low upfront costs, but it brings with it a higher risk of component failure and higher costs on the back end ( negotiating warranty terms). A certain amount of reactive maintenance will be necessary over the system lifetime, but this strategy can be minimized if more proactive PM and condition-based maintenance (CBM) strategies are adopted.

Condition-based maintenance (CBM)

This strategy uses real-time data to prioritize and optimize maintenance and resources, and can be done through third party integrators and turnkey providers. Different CBM regimes have been developed by third parties to offer greater O&M efficiency. However, this comes with a high upfront cost due to communication and monitoring software and hardware requirements.

Routine maintenance Considerations

In general, most PV systems share basic maintenance elements such as modules, inverters, charge controllers, and batteries.

PV module

A thorough inspection of PV modules can be done visually by the owner or installers. Main signs to look for when inspecting a PV system include:

  • Physical damage to frame and glass
  • Delaminating or change in color of the module's outer layer due to separation of bonds between glass and frame that allow moisture or corrosion to seep into the modules

  • Burned connections inside module (hot spots) 

  • Grounding corrosion of wires or frame

  • Array mount weakness or corrosion

Shading control

As we learned in lesson 2, shading can significantly reduce the electrical output of PV array. Even after a careful site evaluation is performed before installing the system, a routine maintenance is recommended to avoid:

  • Soiling

  • Tree growing

  • Leaves and debris accumulation

Battery maintenance

Batteries are considered one of the most maintenance intensive components in the PV system. We discussed in lesson 4 that lead-acid batteries are still widely used in PV systems and a special maintenance attention is needed. A careful consideration and review of the manufacturer’s maintenance recommendations is important to ensure safety on the site.

Electrical Equipment Maintenance

Besides visual inspections of inverters, chargers, transformers, and all other electrical equipment; there are other industry tools that can be used to find the weak points of the system. An infrared (IR) thermometer can be used to find the points where higher temperatures occur, such as circuit breakers, terminals, wires, and others. 

Maintenance plan

A checklist of all required maintenance tasks and their recommended intervals to ensure the best economic scheduling is referred to as a maintenance plan. The intervals can vary according to the site condition and system type. For example, a PV array installed in the desert requires more frequent scheduled cleaning of modules due to dust and soil accumulation.


What is the main cause of system downtime in any PV system?

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ANSWER: Inverters


More information about the recommended maintenance strategy practices in terms of frequency for main elements and main causes of downtime are available for students in Table 3 and Figure 2 on the EPRI report on “Addressing Solar Photovoltaic Operations and Maintenance Challenges: A Survey of Current Knowledge and Practices” posted on the Overview page of this lesson.