Electricity industries worldwide are transitioning away from fossil-fuels towards wind and solar generation. While these technologies are now often cost-competitive as well as environmentally preferrable alternatives to coal and gas options, their highly variable output does raise challenges for delivering secure, affordable, and clean energy. This is particularly challenging for the electricity industries of emerging economies giving growing demand and limited financial resources. This thesis aims to address some of the limitations with existing frameworks, methods, and tools for assisting policymakers to plan electricity industry development, with a particular focus on better assessing future electricity generation options for emerging economies. It uses an open-source evolutionary programming-based optimisation model, National Electricity Market Optimiser (NEMO), to assess future generation options for the case study of Indonesia’s Java-Bali electricity grid. NEMO can model geographically and temporally variable wind and solar resources and solve least cost generation mixes in a highly configurable and transparent manner. A first study assessed the potential industry costs savings possible by recognising the reality of lower reliability standards in emerging economies than often assumed for modelling exercises. Accepting lower reliability outcomes not only reduces industry costs but also supports greater solar and wind deployment, hence better environmental outcomes. Next, the underlying evolutionary programming optimisation of NEMO was used to assess not just the least cost generation mix but the wider solution space, including generation portfolios that deliver total industry costs within 5% of the least cost solution highlighted the wide range of possible technology mixes that could potentially deliver a low cost future industry. Finally, NEMO was used to explore the potential implications of high variable renewable penetrations for operating reserves and hence power system security. The inevitability of some periods with both low wind and solar availability means that high renewables portfolios still feature significant dispatchable generation capacity. This means that the power system will generally have greater levels of operating reserves to cover possible plant failures than mixes with predominantly dispatchable generation. In summary, this thesis contributes to better understanding of the challenges and opportunities of deploying possible future high renewables in emerging economy electricity industries.