variavel0=<b>ARNO KRENZINGER</b> - arno@mecanica.ufrgs.br UFRGS
<b>Jean Marc Lafay</b> -  UFRGS
<b>Abstract.</b> This work presents bases for sizing solar energy water-heating systems using gas as auxiliary energy instead of electricity. A heating system mounted using these bases was analyzed through a computerized data acquisition equipment, which is also described in the work. The measured results propitiated some detailed analyses of the thermal behavior of the system, allowing a better understanding of the phenomena included by solar heaters that operate for thermosiphon. The global results demonstrate that the system has great performance and it should be seriously considered as an option in the moment of selecting the water-heating system for a residence or for an industrial installation.
<b>Keywords.</b> solar energy, solar heating, gas heating, hybrid heating.