Appropriate design of off-grid systems in developing countries requires a detailed and accurate characterization of the expected load and energy resources. This chapter begins by presenting the methods commonly used to characterize the load in off-grid systems, including peak load, demand factor, load factor, and coincidence factor. Load estimation methods are presented, including survey and data-driven methods. The data requirements for energy resource estimation are described. Methods for estimating the capacity factor of solar, wind, hydro and biomass are presented.