word of caution.    A very big consideration when going to voice over  is total failure of outside communication when power fails.

Land line phones tend to work when all else fails.  I have the unfortune to live in rural area that is prone to occassional power outages.  Outages have sometimes lasted as long as 14 days when hurricane or an ice storm has struck. How can u report power outage without phone service?  Cell phones are a help.