This website made me reconsider if 99.9999% SLA and always online is really that important for lots of websites. I used to self-host my own server in my own apartment, but gave up on that after my internet provider had their first major outage that lasted almost a week. Also I didn’t want to worry about the fire hazard, or the server going down when I was traveling etc.
But a solar powered server seems interesting, if the batteries could be made fire safe.
IIRC, the USA Social Security Administration’s website operates somewhat like this, because they seem to still do batch processing (a la mainframes) during the evening hours. As a result, they prevent people from logging in so that they don’t get interstitial data about their public pension.