The amount of solar energy received in Iran is estimated at an average of 18 mega joules per square meter per day or around 1016 mega joules per year in the country. This amount of energy is more than 4000 times the total energy consumed in the country. With this amount of received energy and having suitable lands for using the sun and the relatively simple technology of various applications of solar energy, all the energy needs of the country can be provided by using solar energy. Certainly, achieving a high yield requires spending more. Also, in cold regions, reaching a stable system requires the use of various pumps and valves. Therefore, an acceptable system is a system that results in a combination of high conditions, long life, low cost of maintenance and low cost of working conditions. In all existing solar systems, 1 or 2 water storage tanks can be used, provided that an electric element or another heat source is used in one of the tanks to compensate for heat loss resulting from static water. It is obvious that the heat loss caused by one tank is less than the heat loss caused by two storage tanks due to its smaller cross section. In the case of storage tanks, one should pay great attention to their insulation type so that it does not cause heat loss. The use of an auxiliary storage tank or a gas heating system or heating element in times of cloudy conditions will greatly help to compensate for the lack of available heat.