"Against the backdrop of the daunting carbon-neutral energy needs of our global future, the largest gap between our present use of solar energy and its enormous undeveloped potential defines a compelling imperative for science and technology in the 21st century" (Lewis & Norcera 2006). Concurrently, the United States educational system is failing to produce sufficient numbers of students who are well-versed in the study of science, technology, engineering, and math (STEM), ("Rising Above the Gathering Storm," 2007). Designing, building, testing, and collecting/evaluating data from rudimentary and sophisticated student-created solar hot water heating devices presents tremendous opportunities to address both these imperatives in an engaging manner for students across eclectic learning styles. This article begins by describing the history/rationale as well as the science behind the hot water heater system. It goes on to explain the significance of using a project-based approach and how a student-led, inquiry-based integrative STEM education project that began with research and culminated with designing, building, testing, and gathering data from solar hot water heaters ensued. The authors describe how a group of middle school engineers were challenged to develop an alternative to the common electric hot water heater that most of them had in their homes. The task was not to simply build the best, but to develop the most efficient in terms of construction cost to energy output. The design, build, test, gather data, and evaluation process took on several investigations from rudimentary to complex. The article concludes that the need for future citizens to embrace solar technologies is an imperative. K-12 investigations of solar energy via Integrative STEM projects not only enlighten students to its power, but provide motivation to apply science, technology, engineering, and math in an alluring manner.