An analysis of a drier with passive drying-air temperature control for use on farms is presented. The experimental solar drier with a grain capacity of 90 kg has an initial capital cost of pound 601. Semi-skilled artisans can build the drier at half the price if one used local materials. The cost of sun drying, including a 25% grain loss, is and pound 0.01/kg. With delivery of useful energy at pound 0.06/kWh, 300+ kg may be dried in addition at an added cost of pound 0.01/kg. The drier has a payback period of less than 1 year and is cost-effective for a photovoltaic to solar air-heater area ratio of about 0.22.