It should be no higher than 55 degrees c, to avoid the risk of scalding. This is also the most economical temperature
What Temperature Should Hot Water Tank Be Set At?
120 to 140 degrees the higher the temperature the more it will cost. If you have small children then I would keep it lower. Put your hand into the stream of hot water and touch it quickly and see if it feeld too hat!
140 f is a good compromise for household use. 120F is the maximiun for hand washing, and 170f is required for commercial hand dishwashing.