The HP Spectre x360 includes a 57.8 Wh lithium-ion battery, which is slightly increased from the 56 Wh cell in the previous-generation model. This battery is on the larger end of the scale for modern ultraportables, which when paired with Kaby Lake's slight increases in efficiency, has resulted in excellent battery life.
In both our benchmarks and real-world usage, the Spectre x360 lasted long enough for a solid day's work. It outperformed the two other Kaby Lake laptops I've reviewed – the Asus ZenBook 3 and Razer Blade Stealth – by a small but significant margin, although in our new calibrated Wi-Fi test, the x360 only narrowly outperformed the ZenBook 3 in a surprise result.
I think most buyers will be very satisfied with the battery life provided by the x360, especially as the battery is large without adding a significant amount of bulk to the system.