Electric Thermal Storage

Electric thermal storage

When it comes to energy savings the Europeans seem to be ahead of the whole world. This has a lot to do with the lack of resources and the heavy engineering background on the continent. So it is no small wonder that the European countries were the first to use electric thermal storage, or ETS.

ETS is used in conjunction with the off-peak electrical program that most power companies offer. This idea operates on the fact that power companies have tiered rating system for their power costs. The peak rates are during the day and the lowest costs are from 11:00pm to 7:00am when the power companies drop their rates as much as 60%. It is during this time-of-use (TOU) period that the ETS system is activated through a special meter that separates the costs.

During this period electric energy is converted to heat which is stored in high-mass units, or bricks, made of dense ceramic material. During the peak hours the power is shut off and an electric fan begins moving the heat from the brick to heat the home. The temperature is controlled by outside sensors that adjust the amount of power intake by how much will be needed to keep the room at the required comfort temperature.

ETS Room Heating Units

In a simple ETS system heating units are placed in the rooms where the most heat is required: eg. living rooms, foyers and basement rumpus rooms. Each ETS unit contains nine blocks of dense, iron oxide ceramic clay molded to take in a vast quantity heat energy within a very small space. The most common unit is manufactured by Steffes Corporation. Their bricks are 7" by 8" by 1-3/4" and weigh a remarkable 10 pounds each! During the off-peak period the heating coils are switched on by a microprocessor wired into the meter and the energy is transferred as heat into the bricks. The special composites in the ceramic block are designed for long storage and the even flow of heat.

When the bricks in the unit are charged to the maximum the temperature reaches up to 1,400 degrees Fahrenheit. During daily the minimum temperature of the mass is 250 degrees. So that even during the coldest times the bricks never begin heating from room temperature so there is no power lag or heavy use of electricity to get them up to maximum again.     


Each ETS thermal mass is enclosed in a painted, sheet metal cabinet with a two-tier insulation lining on the inside edge. Using this design the bricks can hold onto enough heat to make the room comfortable until the charging period begins again. The outside layer next to the cabinet is a matte of woven material composed of an aluminum silicate mixture. The inside is another, more complex compound which uses the same material as the tiles which protect the space shuttle. As a result the temperature of the outside cabinet never gets hotter than 180 degrees Fahrenheit. To get the thermal energy into the room usually requires one fan and the larger units will come with two.

Hydronic and Forced Air Heaters

ETS forced air systems use the ceramic brick method in a central air system. These heat up in the same manner as the room units except larger fans pump air into the forced-air ductwork. Besides the advantage of bringing the price of electric heat down to or below the price of gas, oil or propane burners the unit does not switch off when it reaches the comfort level. Like a heat pump the fan on the ETS forced-air system works all the time keeping an even c, set by the homeowner, throughout the house. 

The hydronic units use the same ceramic bricks. A heat exchanger transfers the heat from the bricks either to a water or glycol (vehicle anti-freeze) solution. This then is then either transferred with a small pump or by a pressurized tank.

Advantages of ETS Heating

    1. Lower or same price as fossil fuels: There is no mess or, as in oil and propane, delivery worries.

    2. No open flame: The electric wiring and switches are heavily shielded and controlled through a microprocessor.

    3. No oil or propane tank.

    4. No Co2 emissions.

    5. Low maintenance

    6. Very clean

    7. No chimney or venting

However, the front-end costs are high. The units start at around $2,500 installed for the small room units and add $1000-$1500 for larger ones. This makes installing an ETS unit in all rooms a huge investment. As for central air or hydronic systems you can look at double the price of gas or oil. Then you have to add in the cost of the microprocessor and there may be upgrades needed to the electrical panel. As well, the power companies charge around $20 a month for an administration fee to be on TOU.

In addition, if there is power outage in the winter time you may have to look at a backup system to protect the pipes.

Posted by: TrustedPros
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