I tested the battery life using PCMark 10's new Modern Office and Gaming battery life benchmarks. All the notebooks were set to 100 per cent display brightness and had Wi-Fi enabled. The keyboard backlight was disabled.
I tested the battery in Optimus mode, but that didn't seem to help much. Overall, battery life was mediocre. Unfortunately, the Zephyrus S wasn't able to keep up with the ROG Strix Scar III either in the Modern Office benchmark, despite the latter not being a Max-Q laptop either and having a smaller 66Wh battery.
Power consumption numbers were markedly higher than the other notebooks, but they were on par with the Gigabyte Aero 15 OLED XA which features an OLED panel. This is probably due to a combination of factors, including higher clock speeds on the Zephyrus S' GeForce RTX 2070 and the absence of any Max-Q efficiency optimisations.
However, the Zephyrus S is still somewhat more portable than the ROG Strix Scar III. Our portability index takes into account things like battery life, weight, and the chassis dimensions, so the Zephyrus S' svelte form factor helped make up for its middling battery life. In addition, you can charge the Zephyrus S over USB-C Power Delivery, which may help further mitigate battery life concerns.
Thermal performance is decent, but not class-leading. The palm rests do get noticeably warm to touch, but that's pretty much the case with most gaming notebooks. More importantly, they never got uncomfortably hot, although I did notice that the areas to the left and right of the keyboard had a tendency to get quite toasty.
Like most other gaming laptops I've reviewed, the fans can get quite loud in Turbo mode. If the noise bothers you, you can try setting the profile to Balanced or Silent mode instead, but that of course comes at the expense of higher surface temperatures.