That's what I love about solar energy. Its like the only energy source that doesn't boil water to turn a steam turbine, use water to turn a water turbine or use wind to turn a air turbine.
Except for those liquid salt solar plants that boil water ...
That is the smallest scale of self hosting. The server and the client are the same device. It is also the most insecure way as you probably don't have any backups and very limited storage space.
Actually self hosting is the next step when you decide you want 5+ TB of data and have it automatically create backups. Digital storage media degrade pretty quickly and if you just have your movies on a hard drive in your computer, after 5-10 years you might start to lose quality or some files completely.