I performed a test of this product in my kitchen with a 12 oz. cup (porcelain) of hot water (166F) from a hot/cold water dispenser which I immediately placed on the warmer after being on for a couple of minutes. After 30 mins. on the warmer the temperature decreased to 133F and another 30 mins later to 123F. I used a candy thermometer for temperature readings. This was a ventilated room with an open window nearby from about 5 ft. The tea was still very warm and most likely would need to be reheated for those who enjoy a very hot cup of coffee/tea. The product works as advertised as it is not intended to reheat the contents. It is a very convenient product, safe to use and maintain. I am still happy with my purchase.