The performance of a heating system is selected depending on heat consumption in the particular house as well as hot water consumption. In addition to the internal volume of the house, the method of house insulation, the type of windows and doors are also essential. Choosing the right output of the boiler is important in economic terms – a boiler with a very low power does not heat the whole house, but a boiler with a too high performance does not exercise its options and will work with a reduced efficiency. In addition to hot non-potable water consumption, boilers vary depending on user preferences.