In order to determine what heater size is the appropriate one. One needs to calculate the cubic feet size of the sauna room. In order to do so, multiply the (length X height X Width) Once you have the total cubic feet amount. You will add 1KW for each 50 cubic feet of space. For example if you have a 150 cubic feet room size, the appropriate heater to choose would be a 3KW. Choosing the right heater Kilowattage will ensure an appropriate amount of heat will be generated, distributed and conserved throughout the sauna room.