By switching on and off breakers I isolated the furnace as the appliance pulling the power. When shut off at the thermostat, it is not pulling anything. It only pulls power if it is running. The air coming out doesn't seem to stay very warm, but the thermostat says it is getting to the temperature set and it turns on and off like normal. I did notice that the rubber bobby at the breaker box (I hope that's the right term: the black box that the switch is actually on) is warmer than the others. Could this be electrical or so you have ant other advice? My electric bill went from $60 to $400 in one month. I appreciate anything you can tell me. Kristin.

Is it an electric furnace? 7Kw would be an appropriate size furnace for a smaller home.
Do you have a heat pump? Could it be the heat pump is not working, or the outside temps where to cold for it to work? Is this the first winter in this home? Electric heat is expensive, that's why gas and heat pumps are so popular.