There are a number of different factors that can influence the cost of vinyl windows, but the major things include the size of the window, whether it is custom-built, the hinges needed, the cost of installation and the quality of the glass panes within. Unsurprisingly, larger windows will cost more than their smaller counterparts in most cases. In addition, any vinyl windows with hinges, such as casement or awning windows, will cost more than picture windows that stay fixed at all times. Adding in large bow or bay windows are most expensive because they include construction to actually expand the square footage of the home slightly, and they may require general contractors and permits depending on where the house is located. Any window that needs to be built specifically with measurements in mind will be most expensive of all, but customized windows can add interest or fit in with historic homes. Finally, the quality, efficiency and thickness of the glass panes within the window will affect the total price of the project.