Not sure what you are asking. In order to keep a tetsubin warm/hot, you'll need a hot plate. If, on the other hand, you are talking about an iron teapot that is lined in enamel (think Teavana), well that's different. I don't have any experience with them, but it is my understanding that you cannot use them with heat as the enamel with eventually separate from the iron. All you can do is pour boiling water in them and make tea.