Take a look at the HOSS HE models. I have one and they are great. Be sure that you have a way to unload it if you buy it direct from them, they are extremely heavy. The stoves will start the gasification process in a few minutes and the flue temps are around 320 degrees max. They know everything about the btu requirements per exchanger used. I have never ran out of hot water and heat my house and shop with one load a day with a 500 HE. I went to their manufacturing facility and saw for myself how they make them and it was impressive. They use 1/2" steel to construct the fireboxes and 1/4" steel to form the water jackets in one piece. They even coated the exterior of the units before insulating them. I love mine and know a lot of people that have them. I know guys that have swapped other brands out for the HOSS heaters and say that their burn times doubled at least. The person that i bought mine froms name is Jerry. He was very helpful as well, even after the sale. The company name is Tennessee Outdoor Furnaces and they are located in Shelbyville Tennessee. I went for the HE model because they had one going when i went there heating their plant and their offices and i couldnt see any smoke coming out of the stove and they opened the door and the fire was going gangbusters inside. I looked at almost every model made before I made my decision and I am glad I found them. Over the winter I had three wheelbarrows of ashes at most. I am using it for my hot water now and load it once a week at most. Hope this helps and love this site!