This paper uses both a “top-down” and “bottom-up” economic model to asses the cost and greenhouse implications of various energy and environmental alternatives. The Hawai‘i Computable Generable Equilibrium Model (H-CGE) is a “top-down,” economy-wide model that captures the interaction between both producers and consumers, including full price effects between sectors. The Hawai‘i Electricity Model (HELM) is a “bottom-up” representation of Hawai‘i’s electricity sector. The dynamic optimization model solves for the least-cost mix of generation subject to satisfying demand, regulatory requirements, and system constraints. The models are fully integrated in respect to the electricity sector, where overall economic conditions determine electricity demand and, subsequently, the type of electricity generation has economic impact.