Note that this little program can be used for lots of stuff, but to be on topic, I thought about hugo server – which actually can be fairly battery consuming (I think it’s the “file watching”). So if you have a server running “all the time”, but want to make sure it’s toggled off when you’re off the grid, so to speak:
If you have Go installed:
go get github.com/josharian/power/nobatt
Then, assuming that $GOPATH/bin is in your PATH:
nobatt hugo server
Pretty cool.
Note that it looks like this is currently only supported for macOS.