I've had my NC-13 for a year and half now. Its been good enough to keep up with the demands, of this older house. But not much room to wriggle when it gets below 20 degrees outside. Always was thinking maybe I need to step up to the NC-30 just to give me more options. But didn't want to get the living room too hot either. Its sized to the requirements of my square footage. Well three weeks ago I decided to lay R-19 insulation in the attic (there wasn't no insulation in the attic before this). What a difference it has made on me burning so far. The heat requirements have dropped off quite abit. So instead of burning hard and hot, I can burn with a lower temperature. So thanks for all the encouragement last year to tell me to insulate, just didn't think it would be that dramatic of change. So hopefully this change will carry on throughout the winter.