Automatic Voltage Regulator for Phantoms

[Tubby]

Hi guys,

So we get some power surges and power failures in my area quite frequently. 
Usually I just keep the Phantoms unplugged but I am looking to get an AVR unit for them to give me some peace of mind. 

Anyone have any advice on how many kva the avr should be? 
Should I get one avr per phantom?

They are 2 gold phantoms FYI. 

Thanks