Despite Peterson's comments, Nemertes and other analyst firms have consistently indicated there are many areas of communications cost reductions with VOIP, including savings in adding or moving a phone for an employee or lowering toll-call costs. At new offices, IT managers can sometimes run a single cable instead of two to each desktop, also cutting costs.

Nemertes' research shows that the average cost for one "move/add/change" (MAC) of a phone running on a traditional circuit-switched system is US$124, compared to $10 per move with a newer VOIP system. "Typical MAC costs drop drastically with VOIP," Gareiss said. "So, we're absolutely seeing significant cost savings in some areas."

By running only one cable to a desktop instead of two, installation costs can drop an average of 40 percent, she said. In addition, VOIP customers are seeing drops in the cost of audio- and videoconferencing. Traditional circuit-switched audioconferencing can cost 6 cents to 12 cents per minute, compared with 1 cent to 2 cents per minute with VOIP audioconferencing. Similar reductions are being seen for videoconferencing, which run $200 to $300 per hour for traditional sessions. (Gareiss has not yet calculated the exact cost for VOIP videoconferencing.)

VOIP deployments have also resulted in a need for fewer IT and telecommunications staff. The average reduction on a project is 1.45 people, which might not result in a layoff, but might prevent the hiring of added personnel anticipated with older technology.

In addition to the added costs for time to plan and install VOIP, Nemertes also found that companies are trying to accomplish much more than setting up VOIP, so they find they need to add network management software which they hadn't anticipated early on. "You're not just setting up VOIP in one to two years," Gareiss said. "You're starting an overall convergence project.