While the thermal conductivity is indeed higher for copper than aluminium, it is the heat transfer coefficient that is the characteristic of relevance. The heat transfer coefficient explains how much heat that may be transferred per unit area and is measured in W/(m2K). This means that absorber producers, who use aluminium sheets, compensate with slightly thicker sheets and thereby acquire the same heat transfer characteristics as copper absorbers. It should be pointed out, that the weight and cost of the aluminium solution is still significantly lower compared to copper absorbers.

In an absorber, the tube material heat transfer coefficient only affects a fraction of the total heat transfer, meaning that the performance of an all aluminium absorber is fully comparable with traditional absorbers with copper tubes. The additional thickness of the aluminium tubes compared to copper tubes has no practical influence on the absorber performance. This is because the heat transfer from tube to liquid is the bottle-neck.