Devices that directly capture and store solar energy have the potential to significantly increase the share of energy from intermittent renewable sources. Photo-electrochemical solar-hydrogen generators could become an important contributor, as these devices can convert solar energy into fuels that can be used throughout all sectors of energy. Rather than focusing on scientific achievement on the component level, this article reviews aspects of overall component integration in photo-electrochemical water splitting devices that can ultimately lead to deployable devices. Throughout the article, three generalized categories of devices are considered with different levels of integration, from one-material photoelectrochemical approaches to decoupled photovoltaics plus electrolyzer devices. By using this generalized framework, we describe the physical aspects, device requirements, and practical implications involved with developing practical photoelectrochemical water-splitting devices. Aspects reviewed include macroscopic coupled multi-physics device models, physical device demonstrations, and economic and life-cycle assessments, providing the grounds to draw conclusions on the overall technological outlook.