In an effort to determine if triple-pane windows really are a significant benefit to home energy savings, One Sky Homes, with help from U.S. Dept of Energy's Building America program, compared triple-pane and double-pane window of the same size and same orientation.  The results? Yes, there are energy savings to be had, but the primary benefit is occupant comfort. With even moderate-quality triple-pane windows, occupants are likely to feel very even temperatures in a room, and experience a very high level of comfort, since they are not sensing temperature differentials as they move about a room. Occupants are also less likely to  jack up the HVAC thermostat as they might if they were sensing those differentials.

This YouTube video offers a carefully explained summary of the findings.