Efficiency of the modules are tough to figure. Since my ability to store power is limited, I've given-up on using them as a direct load on the battery unless it is an exceptionally sunny and breezy day. If power coming-in drops off even a little, it doesn't take long to drain the stored energy from the batteries. Instead I'm using the entire fridge unit as a dump load. That is both TEC modules, internal and external fans and the water pump are all used as a single diversion load. This seams to be the most productive setup so far even though the amount of chill it makes varies with the amount of over flow energy it receives. Something I didn't mention in either of these videos, before I added the water cooling system, it had burned-up seven of these 6 amp TEC modules. These were some cheap modules I bought in quantity just to experiment with. I'm using a pair of 9 amp modules in the mini-fridge right now, and they seam to be holding up nicely. The next step to improve the efficiency of the fridge will be a rebuild of the cabinet to something with better insulation.