Interest has been growing in the use of existing pumped hydroelectric (energy)storage (PHS)to follow the increasing variability and uncertainty of intermittent renewable resources, and to add adjustable-speed (AS)PHS capacity to the system as the need for flexible and cheap energy rises. This paper models the operation of AS PHS in the day-ahead energy market. Two optimization models (suboptimization and full optimization)are developed and compared under different renewable penetration levels, while also considering conventional generation cycling costs and network constraints. AS PHS is modeled and tested in the Western Energy Coordinating Council (WECC)system, and the optimizations are demonstrated using MATPOWER software. Results show that full optimization of AS PHS, while considering cycling cost, results in the best AS PHS value, considering energy costs, and AS PHS revenue in renewables-penetration cases.