Today the market offers a variety of heat sources. In some situations, perfectly suited wall-hung boiler, in other cases you will need to install the outdoor units. To correctly select a heat generator for installation in a private house, you must know its power. Usually such information is available after performing precise calculations by experts, but it is assumed that the heating area is 10 squares, you need 1 kilowatt of energy the boiler. To this value must be added about 25% of the required hot water. The final figure obtained after adding another 20% required for the supply of power to the heat source. Material for the manufacture of boilers can be cast iron or steel. They vary in price and weight. The most affordable to houses and other private houses are wall-hung boiler, which operate from both electricity and gas.