On my old laptop, when I was on the bus and wanted to conserve battery life, I'd turn off the wireless adapter.
Although this could be done with a hardware switch on the side of the laptop, I found it was more convenient to do in software.
In Windows, there's a Control Panel page called 'Network Connections' that is quite useful for this:
It seems kind of difficult to find in the Control Panel these days, I didn't see it.
So, you can open the Run dialog (from the Start Menu, or press Win+R), type
and press Enter. This will open Network Connections.
From here, you can create a shortcut on the desktop by finding the little icon to the left of the path (
see the red circle in the figure above), and dragging the icon onto the desktop.
(I found this GUID by opening a Network Connections .lnk shortcut in a code editor to see what was in it).