Lack of access to safe drinking water is a crisis of great proportion. An estimated 1.8 billion people rely on unsafe drinking water. This study focuses on the case of Tanzania, in which an estimated 29 million people, or 44% of the population, lack access to safe drinking water. This study investigates the use of two innovations, solar power and mobile prepayment, to improve water services in Tanzania. User perceptions of innovations are valuable for gauging the potential benefits and barriers to incorporating innovations in the water sector. There are currently no data on user perceptions of these innovations in Tanzania. This study fills this data gap through the analysis of focus group discussions (n=6) and key informant interviews (n=14) collected during summer 2016 in three urban communities in the city of Dar es Salaam, and three rural communities scattered throughout Tanzania. While perceptions varied between urban and rural study settings and within study sites, most people perceived major challenges with the current water system. Research participants generally perceive mobile prepayment as a modern solution to water service challenges, but perceive that cost may be a barrier for the poor. Generally, people in the rural setting perceive that solar power will reduce costs and increase water service reliability, while those in Dar es Salaam were less familiar with the technology. While perceptions indicate that solar and mobile phone innovations have great potential in both urban and rural settings, they also indicate that there exist significant challenges to implementing the innovations. Water sources and water access Multiplicity of sources Source characteristics Urban source changes People rely on different sources for different end uses Cost, convenience, quality, availability Growth in household connections, illicit sources 'Safe' water Water and health Water treatment Bacteria, diarrhea, stomachache, malaria, contamination Waterguard (chlorine-based disinfectant), chlorine, impact of treatment on water taste and odor Perception of water service provider Changing reputation of DAWASCO Need for COWSO training Poor reputation in past (ineffective, nonresponsive, corrupt), but noticeable improvements since 2016 COWSOs are not financially transparent or accountable Training and education to promote change Resistance to change Education and training Members of community resistant to new technologies Education and training needed for people to accept innovations Table 2. Themes, sub-themes, and observations and perceptions of innovations to improve water services. Benefits of mobile prepayment system Familiarity "Modern" and effective Previous experience with mobile payment: Electricity, DART system, and bills Convenient and modern solution, better revenue collection, decreased water theft, fairer system Challenges of mobile prepayment system Network reliability Costs Effect on poor, elderly, and women Mobile money agents Perceived risk of relying on unreliable network to access water services Cost of mob...