that 25 watts was just for ram. You still need another ~5 watts for cpu and display at idle, so you're talking about a laptop that lasts ~3 hours with the screen on literally doing nothing. For comparison, my 2021 XPS-13 (with a pretty small 55wH battery) lasts at least 4 hours under actual use (video playback, browsing github, compiling code etc).
Also, when your laptop is using 25W just for the RAM, that's ~20 watts less that the CPU/GPU get when you want to power up the CPU/GPU.
Also, when your laptop is using 25W just for the RAM, that's ~20 watts less that the CPU/GPU get when you want to power up the CPU/GPU.