I operate a personal server from my office that’s gone down twice in the past month due to a power-out. Each time, it took a while before I realized there was a problem. There is a battery backup, but somehow this just doesn’t cut in quickly enough.
The quick fix was an external uptime monitoring service that notifies me immediately when something goes wrong, namely UptimeRobot.
UptimeRobot’s free plan provides up to 50 monitors and checks server status every 5 minutes. Set up is practically instant, and the dashboard is easy to use. The app’s monitors send an alert by email if a problem arises connecting with a targeted server. The paid plan includes SMS alerts and checks at 1 minute intervals.