A system for mixing and delivering hot water at a user-selected temperature while minimizing consumption of energy and water, having a tank, which has a plurality of chambers adjacently arranged one on top of the other and contiguously connected in series; having solenoid valves on supply lines of cold and hot water to control water inflow to the tank's first chamber; and an algebraic thermometer, placed in the first chamber to send temperature information to a controller which includes a dispenser (metering unit) and outputs an electric signal to the solenoid valves.