HOW DOES IT WORK? The ProgressivTube Passive Solar Water Heater is a self-contained system that combines both the solar collector and storage tank into one streamlined unit. In many setups, it acts as a pre-heater to a conventional or instantaneous water heater, reducing the amount of electricity or gas needed to heat water. In some cases, it can even serve as a stand-alone solution when no backup is required. Once installed, the system runs automatically. When hot water is drawn, solar-heated water flows into the conventional heater—or directly to the tap—cutting down or eliminating the need for traditional energy sources. Of course, performance depends on factors like daily sunlight, weather conditions, and individual hot water usage patterns. Still, even with these variables, solar thermal collectors consistently deliver measurable savings and long-term sustainability benefits.