This paper presents the concept of control ling distributed electric loads with thermal energy storage as apassive electric energy storage system (PEESS). Examples of such loads include different types of thermostatically controlled appliances (TCAs) such as hot water heaters, air conditioners, and refrigerators. Each TCA can be viewed asa thermal cell that stores electricity as thermal energy. Acentralized control mechanism can be used to control thetiming of each thermal cell to consume electric energy so that the aggregated electricity consumption of the thermalcells will vary against a baseline consumption. Thus, when the aggregated consumption is higher than the baseline, the PEESS is charging; otherwise, the PEESS is discharging.The overall performance of a PEESS will be equivalent tothat of a battery energy storage device. This paper presentsthe configuration and formulates the control of a PEESS.The modeling results demonstrate the feasibility ofimplementing the PEESS.