The answer to this question varies depending on your room size. For some context, ALL Insignia steam showers come with a 2.8KW steam generator which is more than sufficient for the size of cabins we have.
If you're building a steam room and it's going to be any bigger than a standard shower size (900x900mm) then we recommend upgrading to the 6KW, 9KW or 12KW. To work out which one of these you need, you need to find out the cubic feet of the room you are creating/have created. Within the description for the heavy-duty steam generators, we have the cubic feet specification so you have access to all the required information so you can make a fully informed purchase.