Or do what I've done. I have an old 2500 watt Onan and I have the furnace set up that I can plug it in to either the mains or an extension cord from the generator. I run a 14 gauge cord from the generator (out in the shed) into the house and plug the furnace in to get the house warm, along with a couple of lamps. Then I disconnect the furnace and run the fridge for a while if necessary. I can plug in whatever I need to run when I need it, and in that way I can limit my loads to 2500 watts. Obviously the kitchen range and the drier cannot be used. My hot water heater is gas, as is the furnace.