solar heater of this invention with no need of installation of external junctions 2 it is protected of the environment avoiding the damages produced by hail objects thrown by the wind dust dirt etc 3 as the panel is surrounded by the inert gas occupying the gap 19 between the dome of the cover 1 and the collector lid 3 the risk of fire is avoided as combustion is not possible in inert atmosphere and further the rust pollution and spoilage are prevented so the photovoltaic panels may be mounted without the protective tempered glass which turns it less expensive and with less weight the photovoltaic panel and the batteries are sized so as to supply electric energy to the pump at least 1 hour daily this is a higher time to the normal operation of the pump for supplying 200 liters of hot liquid at 10 liters per minute equivalent to 20 minutes of daily operation the supporting resistors 13 of fig1 work for ensuring the hot liquid supply in the cases in which the solar radiation is not enough the operation of these resistors is controlled by a microprocessor 13 5 of fig1 provided with an electronic temperature sensor 13 1 of fig2 which senses the temperature within the hot fluid storage tank 8 this microprocessor 13 5 is prepared for controlling the connection and disconnection temperatures of the supporting electric resistors 13 the installed power of these resistors will be determined based on the length of same and thus may be settled according to.