Since their conception, much has been said about the efficiency of evacuated tube collectors. They are commonly heralded around the solar industry as a more efficient collector. If you were just to look at the collector designs, that’s an easy assumption to make. Normally, if you reduce heat losses, in this case by the vacuum of the tubes, you would increase efficiency. So it may sound counterintuitive if I tell you that flat plate collectors are actually more efficient than evacuated tube collectors for all residential and commercial applications even though they are not as well insulated. It takes more than a clever design to produce hot water. It takes a system that is appropriately designed to do what you want it to do. The measure of a collector’s efficiency should really be how they perform when they are put to use.