If I Really Wanted to Build One
If I Really Wanted to Build One
If I were going to build one, as the original poster is interested in doing, then I would consider paralleling Electric Unit Heaters, such as are found in the Grainger catalog, Stock Numbers 3UF75 through 3UF98. They range in size from 3 KW to 50 KW and include the heat exchangers and fans to get rid of the heat.
Different sizes could be selected to get a wide range of loads. Just switch in the ones you need to make the load.