I asked around and found there is liability and legal issues about how you hook up. My furnace is off peak electric, but the fan is on the regular circuit. The furnace has about 1000 lb of ceramic brick that supposedly heats the house for three days. Hmmmmm, maybe in Texas, but it's made in Dickinson. So I paid $1000 to have an electrician hook it all up. He put in another box that turns off the main breaker box when turned on. I only have a 3000 watt Honda so I can only run three of the new boxes six circuits at one time. It's push button so switching circuits is easy. He also wired in a special plug in on the outside of the house, and made a 30 ft heavy 50 amp cord.
I have a gas fireplace in the basement, and a wood fireplace upstairs. If a cord of wood isn't enough I had 11 trees go down this summer and the logs are still on my yard. I think this latest ice storm took down enough large branches to heat my house for a couple weeks. Anyway, the gas fireplace has a fan, and we hooked the furnace fan to the same circuit to distribute the heat around the house. The wood fireplace is one of those with the efficient insert so it will about cook you out of the living room if you don't cut its air a bit. So I can run heat, the freezer, but he refrigerators, and the large TV in the family room with two circuits and choose between the other four.