We live in a drafty old house. It was built this way in part due to most of the year it is so hot here. That was the idea in the 1920's. I saw this heater built with two terra cotta pots, four tea lights, and a loaf pan. I figured I would try it. There is a terra cot pot with the hole covered that sits on top of the loaf pan and then the bigger one sits over it. There are four tea lights that sit in the loaf pan.
We were told it would raise the temperature in a room ten degrees. I am not sure it did but I do think it helped my drafty corner not feel quite so chilly. Since we let the Tall Short Person borrow the space heater that usually sits in my sewing space, I am trying this heater in there with eight candles. I find I lean over and warm my hands on it. That alone is lovely! You could definitely put a mug of tea on top of it to stay warm once the pots are warmed up. It does take a bit.
We will just have to see how it goes.