Voip phone service is good for giving you lower phone rates for calls but if the electricity goes out there is no phone battery to use for back up until it comes back on. Until than you're stuck. I think the F.C.C should do something about this to be honest. So think twice before you switch from Verizon regular phone service to Comcast, Vonage , ViaTalk etc.
One thing, if your electric goes out with Verizon's traditional phone service you pretty much have phone service with no interruptions.