This short article from DefenseTech indicates that the Navy expects to save 24% per year on it's $4 billion dollar telephone bill by switching to Voice over IP phone systems. In round numbers, that's about $1 billion a year, or enough to buy an entire aircraft carrier in five years. Businesses are consistently seeing that much savings or more, and reports of 40% savings are common. Of course, you have to have a reliable broadband connection to switch your business to VoIP.