t is possible that in the near future, energy engineering will be called upon to help society adapt to permanently constrained fuel supplies, constrained green house gas emissions, and electricity supply systems running with minimal capacity margins. The goal of this research is to develop an analytical method for adaptive energy systems engineering within the context of resource constraints. The method involves assessing available energy resources, environmental and social issues, and economic activities. A spectrum of development options is identified for a given region and a Reference Energy Demand is calculated for each representative level. A spectrum of conceptual Reference Energy System Models is generated for each development level with a range of renewable energy penetration. The outcome is a matrix of energy system investment and resource utilization for the range of energy service level defined by the development level. These models are then used for comparative risk assessment. The result is an easily understood visual based investment and risk assessment for both development and adaptation to constrained resource availability. The above approach is being applied to a relatively simple case study on Rotuma, an isolated Pacific Island society. The case study results will show a clear development space for Rotuma where needs and services are in balance with investment, local resource availability and environmental constraints.