All power systems need flexibility, and this need increases with increased levels of wind and solar. There are many sources of flexibility such as from improved system operations, generators, demand, interconnections to other regions, power-to-X, and electrical and thermal. . Energy storage has a pivotal role in delivering reliable and affordable power to New Yorkers as we increasingly switch to renewable energy sources and electrify our buildings and transportation systems. Integrating storage in the electric grid, especially in areas with high energy demand, will. . Local Law 181 of 2019 (LL181) requires the City of New York to conduct a feasibility study on the applicability of different types of utility-scale energy storage systems (ESS) on City buildings and to install such systems on those buildings where cost effective. Various types of energy storage technologies exist. .