Steps for installing and using bower behind a proxy:
Install git, node and add C:\Program Files (x86)\Git\bin to %path%
Then run the following:
set http_proxy=http://<username>:<password>@<host>:<port>/
set https_proxy=http://<username>:<password>@<host>:<port>/
npm install -g bower
Or you can add the following to your .bowerrc file in %userprofile% or in your project