A reliable cooling solution is critically needed but often unavailable in off-grid areas of sub-Saharan Africa, where persistent energy shortages and unstable power supply create a major obstacle for food preservation and storing vaccines. This study demonstrates a practical method for addressing this problem by retrofitting a standard AC refrigerator to run on solar-power using a Variable Speed Direct Current (VSDC) compressor. A 112L Haier Thermocool refrigerator was retrofitted with a ZH15G DC compressor, powered by a 300W monocrystalline solar panel, a 20A MPPT controller, and a 12V, 75Ah battery. The DC system cooled from 25°C to −3.2°C in 9 minutes, consuming 180 Wh/day—91.88% less than the AC system’s 2,217.6 Wh/day. The conversion cost (₦310,000) was 36.7% lower than a new DC refrigerator (₦489,993), with a payback period of 3.55 years and an annual CO₂ reduction of 297.49 kg. Validated by a lumped capacitance thermal model, this scalable, cost-effective solution supports Sustainable Development Goals (SDGs) 7 and 13, addressing energy poverty in off-grid communities.