<p>Solar interfacial desalination (SID), a technology that uses solar energy to produce fresh water, is seen as a potential solution to the twin shortages of water and energy. However, there remains a big gap between the current bench-scale success and future industrial application. Here we show a scaled-up SID system that spans over 150 m² and achieves a fresh-water production rate of up to 4.5 kg m⁻² d⁻¹ and a rated fresh-water productivity of 300 kg d⁻¹ over 4 months of operation. Taking advantage of this large-scale system, we found that the system size requires a dramatic change in materials selection and a substantial increase in thermal mass, leading to a different water yield. A cost analysis revealed that capital investment is heavy, unlike the low-cost operation in indoor SID. We also underscore the importance of addressing fouling, including sedimentation and green algae. By combining a large-scale implementation with an analysis of an SID platform, this work offers insights into its potential for sustainable application in remote areas for domestic water supplies.</p>