Energy storage systems are an important component of the energy transition, which is currently planned and launched in most of the developed and developing countries. The article outlines development of an electric energy storage system for drilling based on electric-chemical generators. Description and generalization are given for the main objectives for this system when used on drilling rigs isolated within a single pad, whether these are fed from diesel gensets, gas piston power plants, or 6–10 kV HV lines. The article studies power operating modes of drilling rigs, provides general conclusions and detailed results for one of more than fifty pads. Based on the research, a generic architecture of the energy storage module is developed, and an engineering prototype is built. The efficiency of using a hybrid energy accumulation design is proven; the design calls for joint use of Li-ion cells and supercapacitors, as well as three-level inverters, to control the storage system. The article reviews all possible options for connecting the system into a unified rig power circuit, and the optimum solution is substantiated. The research into the rig operating modes and engineering tests yielded a simplified mathematical model of an energy storage unit integrated into the power circuit of a drilling rig. The model is used to forecast the payoff period of the system for various utilization options and rig operating modes. The findings of this study can help to better understand which type of storage system is the most efficient for energy systems with temporary high load peaks, like drilling rigs.