Electric Thermal Storage Heat - The Hottest Thing in Maine

When most of us think of electric heat, images of 1960s/70s style buildings with baseboard heaters come to mind. This author lived in one such apartment building in Ithaca, NY where the wall-to-wall carpet matched the baseboard heaters (I don't miss either). In regions without natural gas service, electric heat is seeing a resurgence. Despite naysayers, it really is different this time because modern electric heat technology is vastly improved over the lowly baseboard heaters from years ago. Electric Thermal Storage (ETS) heat is a highly efficient controllable load that can store heat when power prices are low and discharge it during peak hours. This makes ETS heat a valuable resource to grid operators and utilities looking to dynamically balance supply and demand and access a low cost energy storage solution. The advantage to the homeowner is that an ETS heating system can store heat when prices are low (e.g., 2 a.m.) and discharge it later in the day when prices are high (e.g., 5 p.m.), resulting in a lower cost home heating solution compared to oil, propane, or traditional electric baseboard heat.

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There are two types of ETS heating systems. Hydronic systems work by heating a reservoir of water contained in a pressurized tank, typically during off-peak periods. Water has a high heat capacity and if the water tank in the system is sized properly, it will be able to store enough thermal energy to heat a home for many hours without drawing electricity. Some hydronic systems can heat a home for greater than 24 hours without requiring additional electricity. Hydronic ETS systems can be retrofitted onto existing forced hot water, forced hot air, or radiant heating systems. In addition, they can also serve as a supplement to a heat pump system. The other type of ETS heating system consists of ceramic bricks that can be heated to a few hundred degrees Celsius. These bricks are part of a heater module that can be charged up at night (with heat) and discharge heat throughout the day to keep a room warm. One advantage of a Ceramic ETS system is that units can be sized for whatever space they need to heat and they can be a direct replacement for electric baseboards or a supplement for a wood/pellet stove. The graphic above illustrates how a Ceramic ETS system works. The ceramic bricks are shown in red, the circuit board to the right controls the unit (so it only charges during off-peak/low priced times) and the fan at the bottom right pulls air over the bricks and out a vent to supply heat to a room. Dimplex  is a major manufacturer of ceramic ETS heating systems in North America and SmartBricks is a trade name for ceramic ETS systems installed and managed by a Rhode Island company called VChargeVCharge (which resells upgraded Dimplex heaters as well as retrofits for older systems) communicates with its heaters via the Internet to execute energy purchasing strategies that factor in weather reports, grid conditions, and wholesale electricity prices.

Central Maine Power (CMP) recognizes the benefits of ETS heat and they've developed a generous incentive program to encourage its adoption. They have a dedicated webpage for their ETS heat program and will offer a rebate of up to $4,500 for the installation of qualified systems. Many CMP customers, like other residents of Northern New England, do not have access to natural gas and heat their homes using No. 2 fuel oil, propane, or wood. In recent years, the costs of No. 2 fuel oil have risen significantly and heating with oil represents a financial hardship for many Mainers. Propane is also very expensive.

For ETS heat to deliver maximum value to the consumer, its important to have a Time of Use (TOU) rate schedule where electricity is less expensive during off-peak periods (e.g., nights & weekends). CMP offers several residential TOU rates for consumers with ETS heat or those who are energy conscious and willing to shift their consumption to off-peak periods to save money. Currently, CMP offers the following TOU residential rates which are viewable here on the CMP website: Load Management Service; Residential TOU; and Residential Optional TOU. The Load Management and Option TOU rates have subrates within them that customers can pick based on their usage patterns and circumstances. Most people can't bring themselves to read rate tariff schedules in their entirety, but each rate is summarized graphically below and compared to the standard CMP A-1 residential rate which is the default for any consumer who does not choose a TOU rate.

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Generally speaking, the Residential Optional TOU Super Saver rate tends to be the least cost rate choice for ETS heat, although the other listed rates could also be viable depending on the consumption patterns of the house (e.g., occupancy and appliance run schedules). A modern ETS heat system, controlled via the embedded circuit-board will draw electricity during the green (off-peak periods) which is how these systems deliver their cost savings.

In rural Maine, ETS heat systems are competing with No. 2 fuel oil, propane, and wood/biomass. Although electricity powered air source heat pumps are also an option, performance issues in extremely cold temperatures have hindered their adoption in Northern New England. The table below summarizes the various types of fuels, approximate fuel costs, common conversion efficiencies, fuel costs in $/MMBTU of aggregate and usable thermal energy, and the estimated annual cost to heat a typical residential home in Maine. The table shows that ETS heat, while more expensive than natural gas and wood/pellets, has a clear cost advantage over No. 2 fuel oil, propane, kerosene, and conventional electric heat. 

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For Mainers with oil or propane boilers/furnaces near the end of their useful life, ETS heat should definitely be considered if they are CMP customers. For any consumer looking to replace electric baseboard heat or central heating, VCharge hydronic or ceramic ETS systems are a no-brainer and could offer a simple payback of less than two years. The ISO-NE power grid is getting cleaner each year and with all the new wind in Maine, ETS heat systems will be helpful to consume excess wind energy produced during the overnight hours and reduce the high energy costs for home heating in rural Maine.