Solar energy, an option for off-grid energy supply, is often adopted as a solution to limited national grid power supply. The households that use solar energy option have more access to electricity compared to the traditional electric supply-based households so this facility is supposed to increase welfare for households. However, the evidence of the impact of solar energy usage is limited. This study considers vulnerable off-grid households of Kenya as units of analysis, using instrumental variable as identification to examine the impact of solar energy usage on health outcomes, considering gender based heterogeneity. We used dataset prepared by Oxford Policy Management Limited (2021), who conducted Randomized Control Trial in which bi-monthly cash top-up is considered as the treatment variable and solar energy usage is considered as one of the outcomes. In this study, bi-monthly cash top-up (a subsidy) is taken as an instrumental variable and usage of solar energy is the treatment variable. The findings show that the usage of solar energy decreases the health expenditure of user households by 26 percent, indicating better health condition. Heterogeneous analysis shows that solar energy usage has more positive impact on health of female than male members.