I deal with a lot of remote offices located in parts of the world where the local grid power supply is unreliable.

• Power can go off anytime with no warning, with outages ranging from minutes to days
• Power fluctuation is wild, with spikes and brown outs

Currently the offices will have some or all of the following:

• A generator, with an inverter, or some sort of manual switch
• A big UPS or battery array connecting a number of devices
• Several smaller APC UPS with computers attached
• Low cost Voltage Regulators sometimes connected between mains and UPS or device.

I know that each of these things needs to be appropriately rated for the equipment to which it is connected (although I am not sure how to calculate the correct rating).

The offices will generally have the following equipment (in varying quantities):

• some sort of internet connection device (VSAT router, ADSL modem, WiMax router)
• Cisco ASA 5505 firewall
• a bunch of PCs
• printers
• one server

I don't seek to replace the advice of an electrician, but in some of these locations they only answer the questions you ask them, so I need to make sure I have enough understanding of the essentials to protect equipment from damage, and possibly get through some power cuts.