However, sustained penetration will depend on continued technological advances aimed at reducing high capital costs, space requirements and maintenance needs (IRENA, 2015, Kempener et al., The availability of appropriate storage technologies and energy-efficient appliances will also be important to support SHSs for productive uses and rural nonfarming activities. While different off-grid devices provide different levels of energy access (table 3.1), many appliances for productive use, particularly in higher value added stages of production, require medium or high power, and thus upper-tier access.