Jay, my system is built to supply power for my primary electronics, charging of rechargeable batteries, a limited amount of lighting and my ham equipment. This is perhaps 10-15% of my total electrical load today. I am going to have an electrical contractor run extra lines to specific places in my home with different colored sockets so it is easy to tell that they are a part of the off-grid system. My off-grid system will be completely independent and unattached to my on-grid system.
If you want a mobile system I would just build a small, independent one. Two panels with a basic 30-amp charge controller, two batteries and a smaller 1200 watt inverter only runs about $650. I plan to do this on my RV at some point in the future. (Four batteries are just too heavy and bulky to lug around.)