Climate change and global warming are main challenges in modern society. In 2015, 195 countries join the Paris climate agreement, which sets out a global action plan to limit the global warming. To reduce the CO2 emissions, sustainable energy systems play an essential role. Here, we focus on solar water heating systems for domestic use. The aim of this student project is to design, build and test a solar heat system. With this system an amount of water should be heated up as much as possible. This is checked by tapping 1 liter of water from the storage tank at the end of a test cycle, and measuring its temperature increase.