Accelerated market penetration of plug-in electric vehicles (PEVs) is presently restricted by the high cost of batteries. Deployment of grid-connected energy storage, which could increase the reliability, efficiency, and cleanliness of the grid, is similarly inhibited by the cost of batteries. Research, development, and manufacturing are underway to reduce cost by lowering material costs, enhance process efficiencies, and increase production volumes. Another approach under consideration is to recover a fraction of the battery cost after the battery has been retired from vehicular service via reuse in other applications, where it may still have sufficient performance to meet the requirements of other energy-storage applications. By extracting additional services and revenue from the battery in a post-vehicle application, the total lifetime value of the battery is increased, thereby decreasing the overall cost of energy-storage solutions for both primary (automotive) and secondary (grid) customers. In this paper, a techno-economic analysis of second use is described, taking into consideration the effects of battery degradation in both automotive and grid service, repurposing costs, balance-of-systems costs, the value of aggregated energy-storage to commercial and industrial end users, and competitive technology. It is shown that under our chosen assumptions the batteries from PEVs can economically be used to serve the power quality and reliability needs of commercial and industrial end users (e.g., with system payback periods ranging from 7 to 10 years). However, the value to the automotive battery owner is small (e.g., $20-$100/kWh), as declining future battery costs and other factors are expected to strongly affect the selling price. We forecast repurposed automotive battery prices to range from approximately $38/kWh to $132/kWh.