bluGill

No. Federation means I’m on a mbin serner and still interacting with lemmy. If a community goes big there is no way to enforce who goes to which split.

You can maybe stretch that 4 hours to several days. However you must get enough solar in 4 hours to provide more than 1 day of use. You will probably get to 6-8 hours of production from your panels, but the production is reduced in the off hours and there are almost always a few clouds reducing your output even at peak times so until proved otherwise just count on 4 hours. (prove can be several years worth of data, or careful local climate calculation possibly with various devices to handle the sun moving)

How reliable do you need to be - https://solar.lowtechmagazine.com/ often goes offline because there wasn’t enough sun to keep their servers up - would this be acceptable for your servers? (you should spend a lot of time on that website when it is up - it will teach you more than anyone else here)

Will you allow yourself to plug in the backup if there isn’t much sun for a few days (either yourself or some automatic system) - just the ability to go 20 hours on battery and enough solar to recharge the battery in 4 hours on a sunny day would get most people to 90% solar and will be a lot cheaper than chasing to 100% solar all the time - but that might not be good enough for you.

The general rule of thumb if you never can go down is you need to be able to run for 2 weeks without any sun, and enough solar to then recharge those batteries when there is 4 hours of full sun. Of course the weather where you live makes a difference. If you live in the desert your worst possible day will always be followed by a day where you can completely recharge the battery so you need much less batteries; while those who live in arctic locations will not get any sun for a couple months and so need a lot more storage.

Do you mean just Lemmy, or do you also want users from mbin or others fediverse instances that can access lemmy discussions?

There is a point where a forum is too active and you need to either split it or implement weird and complex rules so things don’t get too large.