was kind of hoping for a more analytical take, comparing their efficiency to the newish slate of battery powered personal heaters, or older iron-oxide single us

was kind of hoping for a more analytical take, comparing their efficiency to the newish slate of battery powered personal heaters, or older iron-oxide single use heaters. My guess is the newer electronic devices allow for more consistent heat, but at a much higher entry cost, and less flexible charging. I wonder if an mechanically adjustable thermal barrier could be employed in a hot water device, that could provide a more consistent heating experience.