A professional who evaluates a system at a house will look for the following:
- Is there any broken or damaged equipment?
- Is all the wiring intact and conduit in good condition, with no corroded, sun-damaged, or loose conduit, dangling wiring, or unsecured electrical boxes?
- Is the system working?
- How does the measured power on a sunny day compare to expected output?
- What’s the lifetime energy production of the system and what kind of energy production should you expect in the coming years?
- Is the system monitor (if present) working?
- Is there evidence of animal damage or infestation? Is there sufficient protection for the array wiring?
- Are there any missing bolts, clips, or structural parts?
- Is there mold, dirt, or vegetation buildup on or around the array?
- Are there any remaining warranties on any of the system components?
For battery backup and off-grid systems:
- What is the rating of the batteries?
- What was the load-tested capacity of the batteries?
- What is the age of the batteries?
- What is the general condition of batteries?