I used the built-in battery life benchmark in PCMark 8 Home to assess the battery life on the laptops.
The ZenBook S performed nearly on par with the XPS 13 and both notebooks posted excellent power consumption figures. The ASUS laptop lasted nearly four hours in the benchmark, which consists of tasks such as word processing, email, web browsing and video conferencing. This is the place where nothing beats an LG gram notebook with its crazy long battery life, light weight and very low power consumption.
The portability index is an objective measure of how portable a notebook is, taking into account factors like size, weight, and battery life.
The ZenBook S did fairly well here, coming behind only the Dell XPS 13, which was helped along by its even more compact dimensions. Needless to say the LG gram 13 handily beats anything in its path, but it has been optimized for long battery uptime rather than all-out speed. Placing the outlier aside that the LG is, the ASUS ZenBook S fared admirably. Plus, it's also notably lighter than the Dell XPS 13.