Methods and equipment that were once commonplace may now be unacceptable within the industry, or may not meet National Electrical Code (NEC) or International Building Code (IBC) requirements. The flashing of all roof penetrations is now required by the current IBC. Many older rack systems may not have flashing. While leaks are not common, they occur more often with unflashed systems because the rack feet rely only on sealant to keep the water out—not gravity, as with a flashed foot. If you have a system without flashed feet, it will probably cost a few thousand dollars to upgrade, since the entire array has to be removed along with the old feet.
Another issue is safety and NEC compliance. Most grid-tied systems received building permits and were inspected to allow connection to the grid. But if you are buying an older off-grid system, it is possible that it never received a permit or was inspected. Does it meet Code requirements for wiring, conduit, disconnects, and enclosures? If not, did the installer use best practices for the time, thus making it safe? For the safest operation, systems should be upgraded to meet the Code—so account for this cost when making an offer to the seller. In some jurisdictions it’s not only a good idea, but the law; your system will be required to meet the current Code when the property changes hands. Septic systems and smoke detectors are common items affected by laws requiring upgrades when selling property, but electrical equipment may also be included depending on your local jurisdiction.