There are two main factors that impact the cost of a VoIP phone system. The first cost factor is the number of extensions that you need. This is the cost to purchase, configure, and install each phone, plus a monthly charge for each extension. To estimate your cost of extensions, think about how many employees will need a phone at their desk, and that should be a fairly accurate estimate of the number of extensions you will need.

The second factor is the number of outside lines or call paths that you need. You may have 50 phone extensions, but only 10 of those people need to make phone calls outside the organization at one time. You will need to buy 10 call paths.

There is also a one-time set-up cost of porting your old extension numbers from your existing provider to your new VoIP provider.