Real-world performance of solar water heating systems in West Africa: a multi-site study of domestic and tertiary installations

Solar water heaters (SWHs) have the potential to reduce electricity demand and support energy transitions in sub-Saharan Africa. However, their real-world performance and economic viability remain underexplored, particularly in West African cities, where energy usage patterns and climate conditions are heterogeneous. This study evaluated the technical, economic, and environmental performance of SWHs installed in four distinct urban settings: a hospital laundry and a hotel in Ouagadougou (Burkina Faso), and two households—one in Ouagadougou and one in Lomé (Togo). The systems represent both Sahelian and humid tropical climates, as well as different solar thermal technologies (flat-plate, integrated collector storage, and water-in-glass evacuated tube collectors). Using year-long monitoring data (four years for the hotel), system performance was assessed in terms of solar efficiency, annual energy yield, and CO₂ emissions avoided. A life-cycle cost analysis was conducted under various scenarios to estimate payback periods. System efficiency ranged from 19 % to 41 %, with the evacuated tube collector in Lomé performing best. For household SWHs that replace electric water heaters, the simple payback period was short (2.4 years in Lomé and 2.7 years in Ouagadougou) making them the most economically attractive. In contrast, SWHs replacing gas or charcoal had longer simple payback periods, up to 7.6 years. The highest annual emission savings, 0.98 tCO₂·m⁻², were observed for household applications. Even in challenging environments, thermosiphon-based SWHs have demonstrated substantial energy and environmental benefits. Their broader adoption in West Africa will require improved maintenance, incentive schemes, and adaptation to local fuel prices and context-specific system design.