Infrastructure planning for networked infrastructure such as grid electrification (or piped supply of water) has historically been a process of outward network expansion, either by utilities in response to immediate economic opportunity, or in response to a government mandate or subsidy intended to catalyze economic growth. While significant progress has been made in access to grid electricity in Asia, where population densities are greater and rural areas tend to have nucleated settlements, access to grid electricity in Sub-Saharan Africa remains low; a problem generally ascribed to differences in settlement patterns. The discussion, however, has remained qualitative, and hence it has been difficult for planners to understand the differing costs of carrying out grid expansion in one region as opposed to another. This paper describes a methodology to estimate the cost of local-level distribution systems for a least-cost network, and to compute additional information of interest to policymakers, such as the marginal cost of connecting additional households to a grid as a function of the penetration rate. We present several large datasets of household locations developed from satellite imagery, and examine them with our methodology, providing insight into the relationship between settlement pattern and the cost of rural electrification. (C) 2009 Elsevier Ltd. All rights reserved.