One of the least talked about new features in Photoshop CC 2015 is a brand new export engine that is meant to replace the trusty old Save for Web option.
Looking at the image above you see that Save for Web is missing from the main File menu. There is a new Export option that contains Quick Export as PNG, Export As,the old Save for Web, as well as several other options.
When you use Export As you are presented with a window that is very similar to the old Save for Web, but one that produces drastically smaller files. An initial test exporting the same 2080 x 1386 image saw the new Export As option generate a file that was only 742 KB, meanwhile the old Save for Web option creates a file that is 2,3 MB. That is a tremendous saving of over 50%.
There is one drawback in that Export As will strip away unnecessary metadata and color profiles from the image files it creates. Currently Adobe says these may be added in a future release.