In previous versions, when saving as a template from an Office application (e.g. - .dotx, .pptx, etc.), Office would automatically change the location to C:\Users\username\AppData\Roaming\Microsoft\Templates.
However, in Office 2013 this location is used to store templates from Office.com. To separate personal templates from Office.com templates, the default personal location was moved to C:\Users\username\Documents\Custom Office Templates. All Office applications will save templates to this folder by default.
You can choose to override this setting by specifying a Personal Templates Folder. This can be done by going to File > Options > Save and manually entering a folder path. This needs to be done for each application, and for any application that does not have a Personal Templates path manually set, Office will create the Custom Office Templates folder the first time you save a template, and will set the Personal Templates path to this location.