How much is the size of a minimal Tex Live installation to enable me to write and run TeX in TeXworks in Windows 8.1 (64 bit)? Given the size of Tex Live installation program (install-tl-windows.exe) which is about 12 MB, I assume it shouldn't be more than 20 mb of download. But, I am not sure, and I need to know this because of my bandwidth limitation.
The absolute minimum size for a TeX Live installation is very small: most of the Windows installer is made up of support utilities that are not built-in to the operating system but are used by the installer. I've discussed the approach of building up a minimal system in Why can't TeX Live's size be reduced?: basically you can install just the underlying architecture and add on what you need. Installing the TeX Live minimal scheme with no documentation or sources comes out at 64 Mb, with about half made up of the
texmf-dist tree. One could get that down by selecting only the tools required for a particular task and dropping fonts. For example, I get about 24 Mb of binaries, so if you don't need say XeTeX, dvipdfmx, etc. you can reduce that. However, the effort versus the payoff is not a great balance unless you are looking at a very restricted system. (I have done this for automated testing, where everything installed has to be explicitly justified: that's pretty unusual.)