we have had a record cold winter here, but I have 3 incys and a sportmans hatcher running , so can feel your pain. I also have 6 homemade water fountain heaters running, . I don't use heat lamps, just regular 100 watt bulbs, .I brood in my basement, but move out to unheated buildings with same 100 watt bulb and covered area to get under at about 3 weeks. I would say on average all the extra load added 30 dollars or so a month to my bill, based on previous years kilo watt load. I am working on a better water system for next year, along with a heated nest box to keep my eggs from freezing. Some days, I would pitch 50 percent of my eggs, and I know that the percent of clears went through the roof , I think that the eggs got cold enough to kill the blastocyst even if they did not crack.