In short: Thermal Energy HQ modular thermal storage tanks currently list from approximately $1,190 to $5,798 per tank, equivalent to roughly $54 to $97 per kWh of stored thermal capacity when rated at a 35°C temperature difference.
Larger tanks generally provide a lower tank cost per stored kWh. The 80-gallon model stores approximately 12.0 kWh of thermal energy, while the 700-gallon model stores approximately 108 kWh.
These figures represent the thermal storage tank itself, not the total installed cost of a complete thermal energy storage system. A complete system may also require a heat source, heat exchanger, pumps, piping, controls, electrical work, installation, and commissioning.
Federal tax credits, state programs, and utility incentives may also reduce net project cost when a project meets the applicable requirements.
Thermal energy storage pricing can be confusing because many published numbers describe very different technologies and project sizes.
Grid-scale molten salt systems, industrial thermal storage technologies, experimental systems, and building-scale hot water storage should not be compared as though they are the same product.
For building applications, commercial hot water, residential domestic hot water, farms, and other distributed energy projects, it is more useful to look at the cost of the storage tank first and then consider the additional equipment required to create a complete operating system.
This guide focuses on modular water-based thermal energy storage and the equipment commonly used around it.
Current published list pricing for Thermal Energy HQ modular thermal storage tanks ranges from $1,190 to $5,798.
List price: $1,190
Storage capacity: 12.0 kWh
Approximate tank cost: $97 per stored kWh
Standing temperature loss: 7–8°F per 24 hours
The 80-gallon model is the smallest module in the current line and can be used in residential and smaller thermal storage applications.
The Residential DHW System specification confirms the 80-gallon tank provides 12.0 kWh of thermal storage at a 35°C temperature difference.
List price: $3,427
Storage capacity: 54.6 kWh
Approximate tank cost: $63 per stored kWh
Standing temperature loss: 3.8°F per 24 hours
The 350-gallon model provides substantially more thermal capacity while lowering the tank cost per stored kWh compared with the 80-gallon model.
List price: $4,464
Storage capacity: 77.0 kWh
Approximate tank cost: $58 per stored kWh
Standing temperature loss: 3.0°F per 24 hours
The 500-gallon model is suited to larger domestic hot water, commercial, and process-heat applications where greater stored capacity is required.
List price: $5,798
Storage capacity: 108.0 kWh
Approximate tank cost: $54 per stored kWh
Standing temperature loss: 2.4°F per 24 hours
The 700-gallon model currently provides the lowest tank cost per stored kWh within the modular line.
Storage-capacity figures above are based on a 35°C temperature difference.
Larger tanks generally become more economical when cost is measured against the amount of thermal energy they can store.
The 700-gallon model stores approximately nine times the thermal energy of the 80-gallon tank while costing less than five times as much.
That reduces the approximate tank cost from $97 per stored kWh for the 80-gallon model to $54 per stored kWh for the 700-gallon model.
Larger tanks also generally experience lower temperature loss relative to the amount of energy stored because their surface area does not increase as quickly as their storage volume.
That does not mean the largest tank is automatically the best choice. Proper sizing still depends on the building's thermal load, available space, charging schedule, heat source, and how much energy actually needs to be shifted.
For detailed dimensions, capacities, filled weights, and other specifications, see the Thermal Tank Comparison and Specifications page.
Thermal storage capacity is based on the amount of heat that can be stored as the temperature of a material changes.
For water-based storage, this can be estimated using the mass of the water, its specific heat capacity, and the temperature difference between its charged and discharged state.
Water has a specific heat capacity of approximately 4.19 kilojoules per kilogram per degree Celsius.
For example, approximately 350 gallons of water has a mass of roughly 1,325 kilograms. Raising that water temperature by 35°C stores approximately 54 kWh of thermal energy.
Dividing the storage tank price by that usable thermal capacity provides an approximate tank cost per stored kWh.
This is useful for comparing storage tank sizes, but it is important not to confuse it with the installed cost per kWh of a complete system.
Thermal storage capacity changes depending on the temperature range being used.
A tank calculated using a 50°C temperature difference will appear to store more energy than the same tank calculated using a 35°C difference.
That means two vendors can publish very different kWh ratings for physically similar tanks simply because they used different operating temperatures.
When comparing thermal storage products, verify that the storage capacities are based on the same temperature difference.
The Thermal Energy HQ capacities used in this guide are based on a 35°C delta.
Thermal energy storage and battery storage perform different jobs.
A battery stores electrical energy and can later discharge electricity.
Thermal storage stores heat or cold for later use.
That distinction matters when comparing cost.
Water-based thermal storage can be particularly useful when the building's final energy demand is thermal, including:
Battery storage remains necessary when the goal is to provide stored electricity for backup power, electrical equipment, power quality, or other electrical loads.
At the storage-vessel level, the Thermal Energy HQ modular tank line currently ranges from approximately $54 to $97 per kWh of stored thermal energy.
That number should not be directly compared with a complete installed battery system without accounting for the different equipment included in each system.
A complete battery project may include cells, battery management systems, inverters, switchgear, controls, electrical installation, and other equipment.
A complete thermal project may include the storage tank, heat source, heat exchanger, pumps, piping, controls, and installation.
For a deeper comparison, see Thermal Energy Storage vs. Battery Storage Cost.
The thermal storage tank is only one part of a working system.
A complete project may include several additional components.
The tank stores thermal energy until the building or process requires it.
The storage tank must receive thermal energy from somewhere.
Depending on the application, this could include:
A heat exchanger transfers thermal energy between the stored water and the building's domestic hot water, heating loop, or process.
The specific heat exchanger design depends on the temperature, flow rate, application, and required heat-transfer rate.
Thermal systems can require circulation pumps, piping, valves, fittings, insulation, and related mechanical equipment.
Plumbing requirements can vary considerably between projects.
A control system can manage tank temperature, heat-source operation, charging schedules, monitoring, and system performance.
Controls become particularly important when thermal storage is being used to shift electricity consumption from expensive periods to lower-cost charging periods.
Heat pumps, pumps, controls, sensors, and other system components may require electrical connections.
Electrical requirements depend on the equipment selected and the existing building infrastructure.
Mechanical and electrical equipment must be installed, connected, tested, and commissioned before the system enters normal operation.
This is why the published price of a thermal storage tank should not be treated as the price of a complete installed system.
Thermal Energy HQ's Residential DHW System illustrates the difference between a storage tank and a complete thermal system.
The platform combines an air-to-water heat pump, stainless-steel heat exchanger, 80-gallon thermal storage tank, and control dashboard.
The storage tank itself provides approximately 12.0 kWh of thermal storage capacity at a 35°C temperature difference.
The system's heat exchanger is an immersed closed-loop corrugated stainless-steel design.
The heat pump uses a variable-speed inverter compressor and operates from a 120 VAC, single-phase electrical supply.
The system's dashboard provides live system information, historical usage, estimated savings, alerts, and other monitoring capabilities.
This is why the $1,190 published price for the 80-gallon storage tank should not be interpreted as the cost of the complete Residential DHW System.
The complete system contains substantially more equipment.
Site conditions can have a significant effect on installed project cost.
Major factors can include:
Modular construction can make some installations easier.
For example, the 80-gallon Residential DHW System tank is designed so its components can fit through standard doorways. The specification lists the assembled tank at approximately 63 pounds empty and approximately 730 pounds when full.
The accompanying heat pump weighs approximately 96 pounds and operates from a standard 120V circuit.
The tank and heat pump can also be located separately when the project's plumbing design allows it.
These characteristics can simplify equipment access compared with large factory-assembled vessels, although actual installation cost will still depend on the individual site.
Some projects combine multiple thermal-system components into a packaged configuration.
This can reduce the amount of equipment that must be selected individually and can simplify system design.
For larger packaged configurations, see the All-In-One Thermal Energy System.
For residential domestic hot water applications, see the Residential DHW System.
Operating cost depends primarily on two things:
All thermal storage systems lose some heat over time.
Published temperature-loss figures for the Thermal Energy HQ modular line range from approximately 7–8°F per 24 hours for the 80-gallon tank to approximately 2.4°F per 24 hours for the 700-gallon tank.
How much that loss costs in dollars depends on the tank temperature, ambient conditions, heat source, energy rate, and system operation.
Thermal storage can also reduce energy costs by moving electricity consumption from one time period to another.
For example, a heat pump can charge a thermal storage tank during a lower-cost electricity period.
The building can then use that stored heat during a more expensive period instead of operating the heat source at that time.
Consider a 350-gallon tank with approximately 54.6 kWh of thermal storage capacity.
If the difference between the charging-period electricity rate and the avoided on-peak electricity rate is $0.10 per kWh, shifting 54.6 kWh would represent approximately:
54.6 kWh × $0.10 = $5.46
That means one theoretical full shift across that rate difference represents approximately $5.46 in energy-rate value.
Actual savings will depend on factors including:
The calculation should therefore be treated as an illustration rather than a guaranteed savings figure.
Thermal storage can also be charged using energy produced on-site.
For example, a project may use solar energy during the day to produce and store heat for use later.
The economic benefit depends on what would otherwise have happened to that solar generation.
If the electricity would have been curtailed or exported at relatively low value, storing it as useful heat can increase the value captured from the solar system.
If exported electricity receives meaningful compensation, that export value should also be included when comparing charging strategies.
For more information about scheduling and automated charging, see Smart Thermal Energy Storage Systems.
The listed equipment price is not always the final net project cost.
Certain thermal storage projects may qualify for federal tax incentives, state programs, utility rebates, or other energy-efficiency programs.
Eligibility depends on the specific project configuration.
Federal clean-energy tax law includes certain thermal energy storage within the definition of energy storage technology.
However, that does not mean every thermal storage tank automatically qualifies for a federal tax credit.
Eligibility can depend on the equipment, project configuration, ownership, placed-in-service date, labor requirements, sourcing requirements, and other tax rules.
Projects considering federal tax credits should confirm eligibility based on the complete installed system rather than assuming the storage tank alone qualifies.
California's HEEHRA program can provide incentives for qualifying electrification projects in multifamily properties.
Central heat pump water heating is among the measures that may qualify under the multifamily program.
Program eligibility depends on factors including household income, property type, equipment, project design, and available program funding.
Because incentive availability can change, projects should verify current program status before using rebate amounts in a financial model.
California Revenue and Taxation Code Section 73 provides a property-tax exclusion for qualifying active solar energy systems.
Certain energy-storage equipment can potentially be considered part of an eligible solar energy system when it meets the applicable requirements.
A thermal storage tank should not be assumed to qualify simply because it can be connected to solar equipment.
Eligibility depends on the overall project configuration and the applicable California rules at the time the system is completed.
Utilities can also offer efficiency, electrification, load-management, or custom incentive programs.
Programs vary by location and can change over time.
Commercial and multifamily projects should check the current programs offered by their local electric and gas utilities during the design process.
There is no single installed price that applies to every thermal energy storage system.
For the Thermal Energy HQ modular tank line, published tank pricing currently ranges from:
$1,190 for an 80-gallon, 12.0 kWh tank
to
$5,798 for a 700-gallon, 108.0 kWh tank
That is approximately $54 to $97 per kWh of stored thermal capacity at a 35°C temperature difference.
A complete system can cost more because additional equipment and installation are required.
The final price depends on the heat source, heat exchanger, pumps, controls, piping, electrical work, site conditions, and installation requirements.
At the storage-tank level, Thermal Energy HQ modular water-based tanks currently range from approximately $54 to $97 per kWh of stored thermal capacity when calculated at a 35°C temperature difference.
This is tank pricing, not complete installed-system pricing.
Thermal storage can provide a lower-cost storage medium when the energy ultimately needs to be used as heat.
However, thermal storage and batteries perform different functions.
Thermal storage does not provide general electrical backup power, so the two technologies should be compared based on the load they are serving rather than cost per kWh alone.
Major variables include:
Retrofit projects can vary significantly depending on how much existing infrastructure can be reused.
Potentially.
Certain projects may qualify for federal clean-energy tax credits, state electrification programs, utility incentives, or solar-related programs.
Qualification depends on the complete project configuration and the requirements of the individual incentive program.
Operating cost depends on thermal losses and the cost of the energy used to charge the system.
Thermal storage can improve project economics when energy is stored during lower-cost periods and used during higher-cost periods.
Actual savings depend on the utility tariff, heat-source efficiency, thermal losses, building load, and operating strategy.
Thermal energy storage can provide relatively low-cost energy storage when the end use is heat.
For the current Thermal Energy HQ modular tank line, published storage-vessel pricing ranges from approximately $54 to $97 per stored kWh, with larger tanks providing lower tank cost per unit of thermal capacity.
But tank price is only one part of a complete project.
Heat sources, heat exchangers, pumps, piping, controls, electrical work, installation, and site conditions all affect the final installed cost.
The most useful way to evaluate a thermal storage project is therefore to start with the required thermal load, determine the amount of storage needed, identify the charging strategy, and then price the complete system around those requirements.
For a project-specific estimate, Thermal Energy HQ can help evaluate the building's thermal load, storage requirements, heat source, and operating strategy.
Tell our team about your building, operating goals, and energy needs.
