There are many different components to “servicing.” You have:
In most cases, the system owner is responsible for cleaning and maintenance. If you purchase your installation outright, you’ll have to take care of these activities. If you lease your installation from a 3rd party, that individual is responsible for regular upkeep.
Whether you own the system or lease it, solar panel installers are usually the ones who take care of major repairs. The only difference is who receives the bill. If you’re the owner, then you have to cover these fees out of pocket. If you lease your system, the 3rd party owner will pay for all major repairs.