Systematic efforts to promote box solar cookers in Gujarat (India) began in 1979. Gujarat is characterised by high insolaiton, high ambient temperatures, clear sky and in most parts, sever shortage of fuel-wood. In short, a region with high potential for use of cooker. In addition it has good entrepreneurial climate, an added positive feature. Yet, only about 35,000 units have so far been sold and sales are levelling off. The first-purchase-volume curve, often used by market research professionals to study product life cycle, indicates that cooker is past maturity and is in decline. Significant improvement would be essential for further diffusion. A survey of users in and around Ahmedabad city indicated that they would like the present cooker made less vulnerable to climatic factors. Conjoint analysis indicated two other features desired-doneness indicator, and stainless steel vessels. In this paper we present an analysis of back-up required in Ahmedabad region, which can make the cooker less vulnerable to climate.