Lime12121 said: I recall. I think it was in SSiB that Sakuya appropriated it for making tea.
In the Kourindou LN, in the chapter where Rinnosuke upgrades the Mini-Hakkero, it's mentioned that it has what is essentially a miniature air-conditioning system so that its user can get a gentle spring breeze whenever they want.
This is, of course, in addition to its primary function as a furnace with an adjustable power level ranging from "warming water to make tea" to "Starlight_Breaker on steroids, angel dust and bath salts."