I went down this rabbit hole a few years ago. I bought an X220 (tablet edition) when it first came out. I still have it; with an i7 and 8 GB of RAM it quite frankly can still pull its weight despite being released in 2011 or so.
Anyways, when it was new I kinda-sorta became obsessed about battery life and I tried all the tricks: Screen on minimum brightness, wifi and bluetooth disabled, SSD installed, all the options toggled in PowerTOP and tlp-stat[0], I could get that i7 down to just 6 Watts or so at idle, but of course even the interrupts from the keyboard would cause the power consumption to spike upwards. At 6 Watts it would last something like 9 hours, which is great when you're traveling. Pre-download a bunch of API documentation and man pages, and you can hack away on the plane.
Powertop is a great tool that's only been getting better.
I of course do not use that laptop any more; I gave it to my 4 year old daughter and taught her how to launch emacs. She plays a game where she makes fun letter patterns in the scratch buffer and I use a macbook pro as my daily driver. The battery life is substantially better, and I can't wait to try an M1. My wife's XPS can't hold a candle to the macbook as far as longevity is concerned.
[0] https://linrunner.de/tlp/
Anyways, when it was new I kinda-sorta became obsessed about battery life and I tried all the tricks: Screen on minimum brightness, wifi and bluetooth disabled, SSD installed, all the options toggled in PowerTOP and tlp-stat[0], I could get that i7 down to just 6 Watts or so at idle, but of course even the interrupts from the keyboard would cause the power consumption to spike upwards. At 6 Watts it would last something like 9 hours, which is great when you're traveling. Pre-download a bunch of API documentation and man pages, and you can hack away on the plane.
Powertop is a great tool that's only been getting better.
I of course do not use that laptop any more; I gave it to my 4 year old daughter and taught her how to launch emacs. She plays a game where she makes fun letter patterns in the scratch buffer and I use a macbook pro as my daily driver. The battery life is substantially better, and I can't wait to try an M1. My wife's XPS can't hold a candle to the macbook as far as longevity is concerned.
[0] https://linrunner.de/tlp/