Abstract: The solar water heater is one of the most important applications of solar energy because it
affects several areas large consumers of hot water as habitat, hotels, hospitals, barracks,...which can
satisfy the need up to 80 %, it contributes to the reduction of gases greenhouse and energy
conservation. Why the Algeria has implemented a large program for the development of solar water
heaters in different sectors. The purpose of our work is to study the thermal performance of solar
heater through a comparative study between three Algerian sites namely, Algéria, Béchar,
Tamanarasset, The sizing of the installations is made by the software TRNSYS developed by the
CSTB. Their speeds are represented in the form of graph and paintings translating the variations of
every parameter. The obtained result shows that this system has a good efficiency in the site of
Tamanrasset
