The game can take up to 17 GB after installation (excluding the UHD pack which adds more weight).
The from FitGirl Repacks is a highly compressed version of the game that includes the major UHD visual update. This repack is designed to reduce the download size from its original state to approximately 7 GB . Repack Technical Overview Age of Empires II DE HD Pack -- fitgirl-repacks...
Requires at least 2 GB of free RAM (including virtual) for the installation process itself. Enhanced Graphics Pack (UHD) Details The game can take up to 17 GB