I think my room is 14' x 22'. I would love for it to be wider so I could fit more in it! lol 20' x 20' would work well, giving you room to set up a small office space, room for fabrics, sewing machines, cutting table etc. I have all that in mine, except just one LA and one sewing machine which I leave set up all the time.
I do unplug them when not in use.