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Electric Thermal Storage Heating

Electric thermal storage room units provide a clean, consistent source of heat. Ceramic bricks within the units store vast amounts of heat for long periods of time allowing you to get on-peak performance at off-peak electric rates. (Photos courtesy of Steffes).

Richard de Grasse, PE

Electric Thermal Storage (ETS) heating refers to the process of converting electricity to thermal energy and storing it as heat in high temperature, high density ceramic bricks. ETS systems are designed to use low-cost, off- peak electricity, when the demand on the electric grid is low, for heating a home or business 24 hours a day.

In 1971 I was appointed deputy commissioner of the Vermont Public Service Board (PSB) by then Governor Dean C. Davis. I was an electrical engineer and looked forward to serving on the Vermont utility regulatory commission and with Vermont electric utilities. During my term, I became host to an Australian utility regulator named Tom Strickland. It was he who introduced me to electric thermal storage (ETS) heating and electric utility off-peak, nighttime rates. As a result of Tom’s visit, I called around the country and learned that no American electric utilities served ETS heating customers, yet most European electric utilities did. I concluded that ETS heating could be a real opportunity for Vermont home heating using electricity available off-peak at night from the two large Vermont private electric utilities: Central Vermont Public Service Corporation and Green Mountain Power. At the time I don’t recall either New Hampshire or New York offering off-peak electric rates that were competitive with fossil fuels whereas Massachusetts Electric and Connecticut Light and Power did offer off-peak rates, and a number of ETS systems are installed on their systems.

I needed more information about ETS heating and utility rates before advocating it in Vermont. I applied for and received a grant in the 1970’s from the National Science Foundation (NSF) to review ETS technology among European electric utilities. During my review of European ETS heating technology in the 1970’s, I discovered it had been heating European homes since the 1950’s; more than 20 years previously! I deliberately became acquainted with a number of European ETS home heating customers, several large European electric utilities and 3 or 4 ETS heating equipment manufacturers. Under the NSF grant I installed German ETS heating units in several Vermont homes served by Green Mountain Power. The results were good. The ETS heaters worked well, customers were warm and comfortable and electric heat was affordable under the nighttime, off-peak electric rate. I recently checked. Nearly all the early ETS heating systems are still operating satisfactorily today; 30 years later.

After leaving the Vermont Public Service Board, I founded Control Electric Corporation and began to import and sell German made AEG, ETS heaters in electric utility service areas where off-peak rates were available; mostly in New England and Nova Scotia. We installed hundreds of ETS heating systems. As I recall, Central Maine Power (CMP) did not offer an off-peak nighttime rate at that time. CMP does today. CMP now offers a residential rate A-LM, load management rate, which is cost-competitive with fossil fuels for home heating.

I now live in Maine. The question Mainers ask, “what is ETS storage heating technology and how much does it cost to heat my home?” ETS heating technology couldn’t be simpler. That’s why it has been used in homes around the world for more than 50 years. The ETS room heater shown in the picture contains specially molded magnesite bricks which are heated by electric heating elements to 1200 degrees Fahrenheit during coldest nighttime off-peak hours. The magnesite bricks are specially designed and sized to store the heat energy for release throughout the day during both on and off-peak hours. The box insulation is very well designed and made. Home owners can, if they wish, sit on the heaters! The secret is in the bricks and the sizing of the heater to the heat loss of the area to be heated and the available off-peak electric rate. The amount of off-peak electricity purchased from the electric utility and stored in the bricks is controlled by the outside temperature control; more heat is stored on coldest days. The utility electric meter has a special off-peak register to record the electricity used. The heat is released from the box by radiation and convection from an internal fan controlled either by a thermostat in the heater or on the wall of the room.


The room units are most popular and are designed to the heat loss of the area and the length of the daily charging period. A typical 200-300 ft2 bedroom, for example, would us a 240-volt, 2 kW ETS heating unit utilizing an eleven-hour off-peak, night time charging period.

Years ago, I became acquainted with a fellow named Paul Steffes in Dickinson, North Dakota. He eventually founded a ETS heating systems manufacturing company which is now the best known American ETS heating systems manufacturer. As a result of CMP’s very attractive off-peak rate, I reestablished contact with Steffes in an attempt introduce ETS heating systems in Maine.

I started with Efficiency Maine’s Residential Heating System Cost Calculator. The cost calculator uses a residence having an annual heating heat requirement of 23,371 kWh. Using CMP’S A-LM residential eleven-hour daily 8pm to 7am off-peak rate at $0.082 per kWh the annual heating bill would be $1,916. Assuming the same house having the same heat loss, and one gallon of oil equals 36.6 kWh, it would use 751 gallons of oil assuming 85% heating efficiency. At today’s prices oil costs about $3.45 per gallon this equals $2,591 per year. Off-peak ETS heating is $675 per year less than oil. Which means the CMP A-LM residential rate of $0.082 per kWh is equivalent to $2.55 per gallon. Keep in mind that ETS heating systems require virtually no maintenance. ETS heating is wired in place and is not complicated to install. A nearby electrical contractor should be able to install and check the units.

Richard de Grasse has a BSEE and MBA. He lives in Islesboro, Maine. His electrical utility engineering work evolved in Vermont with Vermont electric utilities. After his term with the Vermont Public Service Board, he became a director of the Vermont Public Power Supply Authority and manager of the Stowe, Vermont municipal electric utility.

1 comment to Electric Thermal Storage Heating

  • David Jackson


    I have enjoyed ETS in Maine since moving into our new home in 1991. We were actually featured a number of years ago in one of CMP’s fliers.

    I have a very old, and out of date, American Technotherm system and can no longer easily source replacement parts for it. The biggest failure point has been the squirrel cage fans, but I have had a couple of the coils burn out as well.

    I am looking for a replacement system and am wondering if you know of any other suppliers then Steffes and the Gabarron Ecombi products. It would also be great if I could do a slow replacement as my major concern is with the 6Kw units in my combined living space (Living Room, Kitchen, Dining Room and Loft).

    Looking forward to hearing back from you.

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