Part Four: Miscellaneous Losses
System Availability & Degradation
Part Four: Miscellaneous Losses
System Availability
Suggested Values:
- Aurora sets a default value of 3%, which is the same used by PVWatts.
- In cases where there is an operations and maintenance or fault alert system set up, the availability loss can be as low as 0.5%.
“System availability” is a generic term for when events knock out the system entirely. This includes inverter shutdowns or failures, grid outages, and other events that disconnect the PV system and prevent it from producing electricity for the home. The exact timing and duration of such outages are unpredictable, so the industry approach is to model these as a flat percentage.
Part Four: Miscellaneous Losses
System Degradation
Over time, a system’s components will be worn down and damaged by the effects of thermal expansion and contraction, UV light, and damage from windblown particles.
There are many studies on this topic that have found that degradation depends on the type of wafer (monocrystalline or polycrystalline), the temperature of the installation site, and the materials used in the construction of the panels.
Every manufacturer has different recommendations on where their panels should be used and what the system degradation might be under those conditions. You can use manufacturer production guarantees for a conservative estimate. For example, if a manufacturer guarantees that their panels will have 80% production after 25 years, that is 20% / 25 years = 0.8%/year degradation.
Note: In Aurora, system degradation losses are accounted for at the financing stage (under Systems & Maintenance) rather than under Performance Settings like other loss types.
Further Reading:
