My house is 1700sqft and it's not to much for my house. So far it hasn't cooked us out but I've only had it for a few months. If I load it up it brings the house up 5 to 6 degrees. It will stay hot and ready to reload for a long time so I dont load it until the house cools down a bit.
I'm not trying to sell you on the englander. That's just what I bought after heating with a cheap shelter style furnace for 5 seasons.