Microsoft Surface Laptop Ultra battery life confirmed: 9 hours in video playback, 53 minutes under GPU stress — worse than MacBook Pro 14 despite 27% larger battery. Asus ProArt P16 with same RTX Spark N1X chip lasts 12 hours in playback but drains in 1h09m under load. Both laptops ship with Nvidia’s new Windows AI SoC, the RTX Spark N1X. Which delivers RTX 5070-level GPU performance but fails to match ARM rivals on efficiency. The Asus Zenbook A16, running Qualcomm’s Snapdragon X2 Elite Extreme on ARM, hit 12h40m on a 70 Wh battery, outlasting both RTX Spark machines while using less capacity. In contrast, the Surface Laptop Ultra’s 9-hour runtime required a battery 27% larger than the MacBook Pro 14’s. The ProArt P16 needed a 99.9 Wh cell. 38% bigger than Apple’s, to eke out three extra hours of light use. Under sustained GPU load (GravityMark 1440p, max performance mode), the Surface Laptop Ultra lasted just 53 minutes. That’s 37 minutes shorter than the ProArt P16 and 37 minutes less than the MacBook Pro 14. Which ran for ~1.5 hours on its smaller cell. The Zenbook A16, again, cleared 2 hours. The takeaway isn’t about raw power, the RTX Spark N1X clearly moves AI workloads. But about trade-offs. You get local LLM inference and real-time video upscaling. You don’t get unplugged productivity. Not yet. The Surface Laptop Ultra and Asus ProArt P16 are shipping now. Pricing remains unconfirmed in both US and India, no official figures cited in testing reports.