The icon of the heat meter indicates the heat used at home. There is a triangle button on the heat meter. Every time you press it, a letter or number will be displayed. Just write it down with a pen and paper, and then look it up slowly. The letter Mwh indicates how much heat is used by the family, and also shows the cooling capacity, excess water, inlet water temperature, return water temperature, accumulated stopwatch time, flow rate and so on.