I have the Solar Panels working. The directions at the beginning are somewhat off. First setup your solar panel in sunlight of course. Next hit TAB and make sure the arrow is up on the solar panel in the vicinity and you'll see a battery slot in the panel and insert the battery in this slot. Then attach metal wire to a 2nd truck battery and then with this battery in your hands walk up to the back of the panel and will see option to "Attach". When it attaches it automatically drops to the ground behind the solar panel. Now I set up my solar panels on the roof around the roof hatch leading down inside our base. I have 5 solar panels setup here on the roof placed around the roof hatch that leads down into the base. I have 5 cable reels attached (1 per each panel) and I have them placed close to the roof hatch. Next I take a 4-plug socket doing 1 at-a-time and plug into 1 cable reel and I take the socket down the roof hatch stairs and place it underneath the stairs on the floor It's a very good idea to set these into a pattern left to right allowing you to remember which one is plugged into which solar panel as doing the same with the cable reel layout. Now I have five 4-plug sockets positioned directly behind the roof stairs. Now doing one at a time I take another socket and plug it into the first 4-plug socket and I ran this to the first bedroom door and placed it on the ground right next to the door. Now from this one I ran 4 additional sockets into the member's bedroom and placed 2 on each side. I then took another and plugged into one on the closest side and positioned this at the end doing the same with the other end of the room. I basically cut each room in half with three 4-plug sockets on each half of the room. The amount you will have to use may differ more or less than this. Now what I did while running the hookup was have a construction light nearby to use as a tester. Also too you'll discover that the 4-plug sockets have a bit longer distance than those cable reels. Just something you'll have to test on your own during your solar electric hookup.
Now also too I discovered after a server restart is that each solar panel itself has to be switched back on after every restart.
I didn't get started on my solar panel journey til after the 1.16 game update so whatever bugs you may have encountered in the past may well be in the past.
Good Luck with your solar power electric hookup and one last thing Don't Electrocute Yourself haha.