The ETS unit can be designed as the main forced-air or hydronic heating system for homes or small commercial buildings. It can also be installed as a supplement to another heating system. As a supplement, ETS can increase the overall efficiency of a heat pump system, provide assistance to an electric furnace during on-peak times, replace a duct heater, or supplement a fossil fuel system. ETS systems work by converting electricity at the utility's off-peak times (usually at night) into heat and storing that heat in specially designed, high density, ceramic bricks. Because ETS systems use off-peak electricity, to be maximally economical, their operation is limited to off-peak operation. That means the system must be carefully sized to assure it can hold enough heat to maintain comfort at the coldest temperatures that would occur in the year.
ETS units have control systems that automatically regulate how much heat is stored in the brick core in relation to outdoor temperature and the heating requirements of the user. When the room thermostat calls for heat, heat is extracted from the unit's storage core and is distributed into the home until the call for heat has been satisfied. ETS systems can be integrated with all the common peripherals like an air conditioner, electronic air cleaner, central humidifier, and programmable thermostats.