The Surface Pro X runs on a special chip that gives it impressive battery life, especially for a device that runs a full operating system and desktop apps.
It's a chip made by mobile chipmaker Qualcomm, and it's based on the so-called ARM architecture. In English, it means the Surface Pro X will handily do what most people do on their laptops while offering long battery life. It's the first time a Microsoft laptop is using an ARM-based chip, rather than an Intel processor.
Microsoft boasts a 13-hour battery life during "typical device usage" — two and a half hours more than the Surface Pro 7, and three hours more than Apple claims for its 13-inch iPad Pro. And keep in mind that the Surface Pro X is running the full version of the Windows 10 operating system. It's a full laptop, capable of running any Windows software.
Admittedly, 13 hours seemed a little low at first blush —some industry-watchers were expecting something closer to 20 hours from ARM chips. But that expectation comes from ARM chips that are designed for mobile devices like smartphones and tablets. The custom ARM chip that Qualcomm is making for the Surface Pro X, called the Microsoft SQ1, soaks up more power to deliver computer-like performance rather than smartphone-like performance. As a result, that means less battery life than you'd find on a mobile device.
There's some concern that the Surface Pro X's ARM chip can only run low-powered version of apps (32 bit versus 64 bit). I didn't have enough time to put the Surface Pro X through its paces to see how that affects a normal workflow, so I can't comment on that supposed limitation right now. However, it seems reasonable to assume that while it may not be great for anything intensive, like competitive "Fortnite" or hardcore Adobe Illustrator work, it'll probably be just fine for Microsoft Office, Facebook, and maybe even "Minecraft."