In a controlled environment ranging from 22 to 22.4°C and 60% humidity I poured some tap water in an aluminium cup. Its temperature stabilised at 24.7°C. I placed the cup in the pad at full power. Left it about 7 minutes and checked the temperature again at 27.1°C. The measurements were taken from a quality digital thermometer for patisserie purposes able to collect data from -40 to 220°C. The pad works, if I left it for 10 mins or more it would go even higher, maybe it's not that fast for some