I don't trust their battery run-times. I was looking for a laptop and finally settled down for a Lenovo Thinkpad 13.
Thinkpad's battery is 42 Wh with a wifi surfing run-time of almost 7 hours [0], although it being sold as a 11 hours run-time. It hasn't a dedicated graphics chip.
Xiaomi's battery is 40 Wh and it sports dedicated graphics. Macbook Air's battery is 58 Wh and it has integrated graphics, lasting around 10 hours [1].
Assuming a similar consumption, Xiaomi's would last less than 7 hours for surfing. But it has dedicated graphics (NVidia 940M) with a consumption (30W) that doubles integrated options (Intel HD in Lenovo and Apple laptops). So, probably it will last 5 or 6 hours of just wifi surfing, even less.
Laptops with discrete GPUs tend to have an integrated GPU as well, and keep the discrete GPU powered off most of the time. The 30W you quoted is the maximum power consumption for the discrete GPU, when it is active and running at full tilt.
The battery claim may be for the smaller model, which uses a Core M (similar to the new Macbook). That wouldn't be comparable to the Thinkpad or Macbook Air at all.
Thinkpad's battery is 42 Wh with a wifi surfing run-time of almost 7 hours [0], although it being sold as a 11 hours run-time. It hasn't a dedicated graphics chip.
Xiaomi's battery is 40 Wh and it sports dedicated graphics. Macbook Air's battery is 58 Wh and it has integrated graphics, lasting around 10 hours [1].
Assuming a similar consumption, Xiaomi's would last less than 7 hours for surfing. But it has dedicated graphics (NVidia 940M) with a consumption (30W) that doubles integrated options (Intel HD in Lenovo and Apple laptops). So, probably it will last 5 or 6 hours of just wifi surfing, even less.
[0] http://www.notebookcheck.net/Lenovo-ThinkPad-13-Ultrabook-Re...
[1] http://www.notebookcheck.net/Apple-MacBook-Air-13-2015-Noteb...