Linux

The main power draws on a laptop are the display, the GPU, and CPU in that order. If you can't tame the first two, the third won't matter if we're discussing hardware platforms in the past 5 years.

If you can tune one distro to be as power efficient as you like, any of them can do it. There is no functional difference between any of them that is not configurable.

The most power efficient and balanced platform you're going to get is an AMD APU for general work, or something REALLY weak but efficient like the lowest of low-end Intel like the n-series chips.

Anything with Nvidia in it is going to drain your battery quickly, even if not being utilized (that's a hardware design thing I won't go into).

Install and read up on tlp, lower screen brightness and bring powerbanks would be my tips if you wanna use a laptop in the forest.

This isn't really a distro thing. You'll get the best results by turning off radios, ensuring the CPU frequency is controlled (or just locked to the lowest), and not using any 3D stuff or the discrete GPU.

It's a good topic to raise, laptop battery life is definitely still a weak point on Linux. I'm not sure there's any distro specifically geared towards extending battery life, but maybe choosing one with a light desktop environment would help? I'm no expert myself but it also depends on the device you're using and it's platform.

For example, one common power management tool tlp https://linrunner.de/tlp/index.html is not recommended by AMD or Framework for my FW13. There are steps you can take, like ensuring your browser is using the GPU/iGPU for videos/hardware acceleration is enabled and working, but Linux as a whole does not seem to have prioritised improving battery life. It's understandable to a degree, with it being dependent on so many factors