I would suggest either Warrens suggestion of a UPS (and the machine carrying out a graceful shutdown when mains power is lost) or moving to the cloud. Having dealt with sites that use generators the transients caused by generators have crashed (and often killed) devices, (both servers and hardware encryptors) its usually best to avoid the situation. Also nobody has mentioned the potential blame storm should something happen to a server which is located in a domestic location.
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