Access to water for domestic and irrigation uses remains limited across Sub-Saharan Africa, particularly in rural areas. While the technical feasibility of implementing innovative technologies to improve water supply has been often evaluated, less is known about the drivers that motivate users to pay for obtaining the inherent benefits of improved water supply. In this article, the determinants of the marginal willingness to pay (mWTP) for improved domestic and irrigation water are investigated. For this purpose, a contingent valuation study is performed in rural Rwanda. This study uses survey data from 316 households situated in 8 villages, in which ~20 % of the households receive electricity thanks to microgrids powered by solar energy. It is found that the mWTP for improved domestic water supply is influenced by the proportion of children in the household, business ownership, and satisfaction with water quantity and quality. The mWTP for irrigation is determined by respondent education, business ownership and crop area planted. This paper contributes to the literature by allowing a comparison of the determinants of the mWTP for improved domestic water supply to the determinants of the mWTP for irrigation. Another contribution is to examine the mWTP for improved water infrastructure in partially electrified villages. Identifying areas with high marginal benefits from water can guide infrastructure investment and electrification efforts while improving well-being and increasing revenues in rural areas.