This is the most optimal way that you have hot water in the apartment. There are two types of water heaters — this is a flowing and cumulative. Depending on the type and method of heating, they have different. Accumulative water heaters heat the volume that is placed in the tank itself. After the water is heated, it turns off only when you start using it, or it cools. The flowing water heater works differently, it turns on when you turn on the water. It has a very strong heating element, approximately like in an electric kettle that heats the flow of water. Electricity with a stream water heater is consumed many times more than with accumulative.