This will determine who you should first contact if you have a problem with your PV system.
If the original installer is still in business, there may be some time left on their workmanship warranty. This will protect a new homebuyer should there be any problems with the physical work that was required to complete the solar installation, most importantly the penetrations done to the rooftop to attach the system. This provides important protection for any leaks in the rooftop.
If the original installer is no longer in business, you will want to contact a qualified technician experience to service your solar equipment. You may want to ask about a Sunspear Protection Plan which provides 24/7 monitoring and access to a US based call center for any maintenance and repair issues that may arise in the future.