Evacuated tube collectors are made of a series of modular tubes, mounted in parallel, whose number can be added to or reduced depending on the quantity of hot water required. In an evacuated tube collector, sunlight passing through an outer glass tube heats the absorber tube contained within it. The absorber can either consist of copper (glass-metal) or specially – coated glass tubing (glass-glass). The glass-metal evacuated tubes are typically sealed at the manifold end, and the absorber is actually sealed in the vacuum. The glass tubes are directly connected & fitted to the hot water tank.

The working of ETC based solar water heating system is based on the principal of black body absorption. The black surface of the tubes, absorb the heat from the solar radiation and transfers it to the water in the tube. Hot water being lighter than cold water rises to the top of the glass tube and into the hot water tank. This cycle goes on during the hours of sunshine (usually between 10am to 4 pm). At the end of the day the tank is full of hot water at designed temperature.