Ars found their data to be roughly in line with Dell's claim as well, though they only tested the high-res notebook and didn't check the FHD one:
> Dell claims that the battery life of the XPS 13 is an impressive 15 hours for the 1920×1080 model and 11 hours for the 3200×1800 version. Our own battery testing is a little more punishing than Dell's, but the company's numbers seem to be in the right ballpark. In our test of light Web browsing, the XPS 13 came in just shy of nine hours
Usage pattern is definitely a huge factor though:
> in a more intensive WebGL test, it hit five hours on the dot.
and so is software running (using Chrome is a terrible idea if you want battery life, for instance)
> Dell claims that the battery life of the XPS 13 is an impressive 15 hours for the 1920×1080 model and 11 hours for the 3200×1800 version. Our own battery testing is a little more punishing than Dell's, but the company's numbers seem to be in the right ballpark. In our test of light Web browsing, the XPS 13 came in just shy of nine hours
Usage pattern is definitely a huge factor though:
> in a more intensive WebGL test, it hit five hours on the dot.
and so is software running (using Chrome is a terrible idea if you want battery life, for instance)