Regarding knowing when the power comes back, there is a device called the PowerBack by Reliance Controls I got that alarms when the power comes back. If you're not there to turn it off, however, the 9 volt battery will discharge. We had a short power outage the other night and we just hung around in lamplight, but I turned off the main breaker so that power surge, etc, wouldn't hurt anything when the power came back. The siren wailed and I knew the power came back.