Energy poverty is prevalent in resource-limited settings, leading households to use inefficient fuels and appliances that contribute to household air pollution. Randomized controlled trials of household energy interventions in low and middle income countries have largely focused on cooking services. Less is known about the adoption and impact of clean lighting interventions. We conducted an explanatory sequential mixed methods study as part of a randomized controlled trial of home solar lighting systems in rural Uganda in order to identify contextual factors determining the use and impact of the solar lighting intervention. We used sensors to track usage, longitudinally assessed household lighting expenditures and health-related quality of life, and performed cost-effectiveness analyses. Qualitative interviews were conducted with all 80 trial participants and coded using reflexive thematic analysis. Uptake of the intervention solar lighting system was high with daily use averaging 8.23 ± 5.30 hours per day. The intervention solar lighting system increased the EQ5D index by 0.025 [95% CI 0.002 - 0.048] and led to an average monthly reduction in household lighting costs by -1.28 [-2.52, -0.85] US dollars, with higher savings in users of fuel-based lighting. The incremental cost-effectiveness ratio for the solar lighting intervention was $2025.72 US dollars per quality adjusted life year (QALY) gained making the intervention cost-effective when benchmarked against the gross domestic product (GDP) per capita in Uganda. Thematic analysis of qualitative data from individual interviews showed that solar lighting was transformative and associated with numerous benefits that fit within a Social Determinants of Health (SDOH) framework. The benefits included improved household finances, improved educational performance of children, increased household safety, improved family and community cohesion, and improved perceived household health. Our findings suggest that household solar lighting interventions may be a cost-effective approach to improve health-related quality of life by addressing SDOH.

Solar lighting is an alternative to polluting kerosene and other fuel‐based lighting devices relied upon by millions of families in resource‐limited settings. Whether solar lighting provides sustained displacement of fuel‐based lighting sources and reductions in personal exposure to fine particulate matter (PM2.5) and black carbon (BC) has not been examined in randomized controlled trials. Eighty adult women living in rural Uganda who utilized fuel‐based (candles and kerosene lamps) and/or clean (solar, grid, and battery‐powered devices) lighting were randomized in a 1:1 ratio to receive a home solar lighting system at no cost to study participants (ClinicalTrials.gov NCT03351504). Among intervention group participants, kerosene lamps were completely displaced in 92% of households using them. The intervention led to an average exposure reduction of 36.1 μg/m3 (95% CI −70.3 to −2.0) in PM2.5 and 10.8 μg/m3 (95% CI −17.6 to −4.1) in BC, corresponding to a reduction from baseline of 37% and 91%, respectively. Reductions were greatest among participants using kerosene lamps. Displacement of kerosene lamps and personal exposure reductions were sustained over 12 months of follow‐up. Solar lighting presents an immediate opportunity for achieving sustained reductions in personal exposure to PM2.5 and BC and should be considered in household air pollution intervention packages.

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