This article presents a simplified economic analysis of the effect of hourly variations in power costs on energy and capital costs of cryogenic air separation plants. The objective is to see what ratio of peak-to-minimum energy costs is required to make intermittently operated air separation plants economically attractive. The study focuses on super-staged argon-column air separation plants producing both gaseous and liquid oxygen and nitrogen, along with high-purity liquid argon. Preliminary results indicate that power price ratios between about 2 and 7 are required, depending on the process and economic assumptions. The analysis uses thermodynamic ideal-work calculations to predict energy requirements for plants that produce varying amounts of liquid and gaseous products. These products must be provided to customers even when the plant is not running, so excess liquid oxygen and nitrogen must be produced and stored during the period when the plant is running. The actual power consumption of the base 24-hour plant is used to calculate a thermodynamic efficiency (about 33%), which is then used for the modified plants. Capital costs for the conventional continuously operated 24-hour plant are assumed to be some multiple of the energy costs for the 24-hour plant evaluated at the minimum power price (P-min). Capital costs for the 12-hour plant and the 8-hour plant are scaled up from the capital cost of the 24-hour plant. The analysis assumes a three 8-hour power-price-window cost structure. The economics are evaluated over a range of power price ratios. In the most optimistic case, when the annual capital cost for the 24-hour plant is assumed to be 30% of the total annual cost, the equipment cost is scaled using the conventional 0.6 power factor and instantaneous start-up is assumed, the 8-hour plant becomes economically viable at a power-price ratio of 2.13. When the instantaneous start-up assumption is removed and one assumes that only the minimum power price is observed on weekends, the 8-hour plant becomes economically viable at a power price ratio of 4.15.