Over 1.5 billion people in the world today are still without access to electricity with many of them living in rural and remote areas that are far away from the national main grid. A large number of these people are in developing countries located in Africa and Asia. Provision of sustainable forms of clean energy sources including electricity to these people is a continuing global developmental challenge that needs to be addressed. While a number of rural electrification projects have been undertaken in these developing countries, it has been noted that many are not sustainable hence they do not survive beyond the initial donor funding phase. Robust metrics to measure sustainability of such projects are still lacking. In this thesis, research is carried out to examine the sustainability of rural microgrids and then develop metrics to enhance how sustainability can be measured for these types of projects. The research further seeks to formulate and design an optimum, robust, sustainable and economical solar PV based microgrid solution for electrification of a remote area focusing on green areas that currently have no access to electricity. The objective is to achieve a system that is cost effective, reliable and sustainable. First, an examination of the issues surrounding microgrids for rural electrification is carried out with a major focus on the sustainability challenges. Informed by this examination, the important factors to consider when evaluating sustainability are presented and an easy to use sustainability evaluation tool kit is proposed and tested against three microgrid projects. Since establishment of an off-grid rural electrification system requires accurate prediction of the electrical load so as to have a sustainable system that can meet the electrical needs of the community, an evaluation of the efficacy of the current methods for load estimation was carried out as a critical component of this work. An improved load estimation approach that yields more accurate load estimates has been proposed. Load characteristics that take account of the influence of gender as well as changes in customer habits on estimated load are investigated using the Markov Chain process. MATLAB software is used to generate load profiles. The results show that gender considerations have a significant impact on load profiles and a higher consumption is obtained when gender is considered. Next, an efficient and robust sizing approach for off-grid PV microgrid systems has been developed and named the ComÂµGrid Sizing Approach. This approach utilizes "Mixed Integer Linear Programming (MILP)" to optimally size the PV microgrid and the "Density Based Spatial Clustering of Applications with Noise (DBSCAN)" algorithm to aggregate load and meteorological data. MATLAB software is used to execute the optimization algorithm. The results show that the proposed method yields a reliable and less expensive system and that it is possible to achieve accuracy and a faster convergence to the solution with this approach. Lastly, an investigation of affordability of community microgrids is carried out since affordability is essential for their sustainability and effective utilisation of the services they offer. The critical elements that have to be considered when designing microgrids for rural communities are addressed with the aim of reducing the overall cost of electricity.