If your router reverts to factory defaults after losing power, I would think there is a problem with your router. There should be only TWO ways to get a router back to factory default. The first and easiest is the button on the back that you push in with a safety pin, and the second, is generally an option to do so within the router's configuration.
If you aren't using the wireless, you could also remove the antenna. Many of them just screw off the back. That should limit range to within your home/business.