An Overview of Ice Thermal Energy Storage Systems and Peak Demand Management

Managing energy costs in large commercial and industrial facilities requires more than just securing a competitive rate. It requires a strategic approach to how and when your facility consumes power. For many businesses, cooling represents a significant portion of their overall energy consumption. On hot summer days, air conditioning systems across the country are cranked up to keep occupants comfortable and critical equipment safe. This concentrated usage creates a surge in energy requirements known as peak demand.

As energy demand increases during these afternoon hours, the electric grid experiences significant strain. In response, energy costs typically rise. Facilities that draw heavy power during these periods often face high demand charges on their utility bills. Peak demand management is the practice of strategically adjusting your facility’s energy use to reduce consumption during these high-cost, high-stress periods. While there are many ways to approach peak load management, an overview of ice thermal energy storage systems reveals one of the most effective, long-term solutions for shifting cooling loads and driving operational efficiency.

Understanding Peak Demand and Cooling Challenges

To effectively manage energy costs, it is important to understand the difference between overall energy consumption and peak demand. Consumption is the total amount of energy your facility uses over a billing cycle. Peak demand is the highest amount of power your facility draws at any single 15-minute or 30-minute interval during that same period. Commercial utility rates often include demand charges based on this peak interval. If your heating, ventilation and air conditioning (HVAC) system kicks into high gear during a hot summer afternoon at the exact same time your operational equipment is running, your peak demand spikes. This single spike can dictate a large portion of your monthly energy bill.

Cooling is a primary driver of these peaks. Traditional HVAC systems must generate cooling at the exact moment it is needed. Because peak cooling needs align perfectly with peak daytime electricity rates and maximum grid congestion, facilities are forced to purchase energy when it is most expensive. Overcoming this challenge requires separating the creation of cooling from the delivery of cooling.

What is an Ice Thermal Energy Storage System?

Ice thermal energy storage systems, sometimes referred to as “ice batteries,” provide a mechanism to decouple the generation of cooling from its consumption. These systems act as a long-term load-shifting strategy for facilities with meaningful cooling demand. Instead of relying entirely on daytime HVAC operation during high-demand periods, the system creates stored cooling overnight when energy demand is low and rates are typically more favorable.

While thermal energy storage systems can use either ice or chilled water as the cooling medium, ice is much more common. Ice absorbs eight times as much thermal energy as chilled water, making it a highly efficient medium for storing cooling potential in a smaller physical footprint.

The market for this technology is expanding rapidly as businesses seek practical pathways to manage high demand charges and support grid reliability. According to Allied Market Research, the global ice thermal energy storage market is expected to grow from $193 billion in 2024 to $443 billion in 2030. This growth reflects a broader industry shift toward advanced peak demand management solutions that deliver tangible cost savings.

How Ice Thermal Energy Storage Works

The operation of an ice thermal energy storage system relies on a predictable daily cycle of charging and discharging thermal energy.

During off-peak hours, which typically occur at night, the facility’s chiller operates to freeze water inside a specialized storage tank. Because overall energy demand on the grid is lower at night, the electricity used to run the chiller is less expensive and more abundant. The ice is created and stored in highly insulated tanks designed to minimize melting and maintain maximum cooling potential until it is required.

During the day, especially during peak hours when cooling demand is highest, the system transitions to its discharge phase. Instead of running the energy-intensive chiller to cool the building, the system circulates a heat transfer fluid—such as water or glycol—through the ice storage tank. The fluid is cooled by the stored ice and is then distributed through the building’s existing air conditioning system to provide comfortable, consistent cooling to occupants and equipment.

These systems generally fall into two operational categories:

• Full storage systems: These systems shift the entire cooling load to off-peak hours. The chiller only runs at night to build ice, and the melting ice handles 100% of the building’s cooling needs during the day.
• Partial storage systems: In this configuration, a smaller chiller works in tandem with the ice storage system. The chiller runs continuously during both peak and off-peak hours. At night, it builds ice. During the day, the chiller provides a baseline level of cooling while the melting ice supplements the system to handle the peak cooling load. This is often an attractive option when a facility needs to add cooling capacity or when an aging chiller requires replacement, as it allows the facility to purchase a much smaller, less expensive chiller.

Financial and Operational Benefits

The primary advantage of implementing an ice thermal energy storage system is the ability to drastically reduce peak electric demand. By taking the heavy load of daytime cooling off the grid, businesses can see significant reductions in demand-related energy costs.

Real-world applications demonstrate the profound impact of this load-shifting strategy. The Eleven Madison skyscraper in New York City utilizes an ice storage system to cool its massive footprint. Every night, the system generates approximately 500,000 pounds of ice. To put that volume into perspective, it is enough ice to fill three city buses full of ice cubes. By using this stored thermal energy during the day, the system can lower the building’s cooling costs by up to 40%.

Healthcare facilities also benefit greatly from reliable, cost-effective cooling. Norton Audubon Hospital in Louisville, Kentucky installed an ice thermal energy storage system featuring 27 tanks. These tanks sustain a network of cold water pipes that help keep operating rooms at safe, precise temperatures while keeping patients comfortable. Every night, the hospital freezes roughly 74,000 gallons of water. In the first year the ice storage system was in operation, energy costs at Norton Audubon were $278,000 lower.

Integrating Thermal Storage with Broader Load-Shifting Strategies

While ice storage is a highly effective long-term load management investment, it works best when integrated into a comprehensive energy strategy. Facilities can significantly lower energy costs by combining thermal storage with simple, low-cost strategies to shift electricity load away from peak periods.

Facility managers can reduce stress on the grid by adjusting temperature settings slightly higher in occupied zones. Resetting chilled water temperatures slightly higher and utilizing variable speed drives on HVAC fans and compressor motors can further reduce electricity use during peak hours. Additional strategies include reducing lighting levels in common or low-traffic areas, turning off lights in unoccupied spaces and enabling power management sleep settings on all office equipment. Industrial facilities might schedule the charging of battery-powered equipment for overnight hours or shut down ancillary equipment like compressors during the afternoon.

Using an ice storage system also positions a facility to maximize the value of demand response programs. Traditionally, energy companies managed grid growth by building expensive power plants that might only be used to cover a few peak hours on the hottest days of summer. Demand response programs offer a cleaner, faster alternative by paying customers to temporarily shift or shut down equipment during peak periods.

Because an ice storage system automatically shifts the cooling load to off-peak hours, participating facilities have more flexibility to reduce their daytime energy profile without sacrificing comfort or operational continuity. Whether participating in capacity reduction programs that pay specific incentives for pre-committed load reduction or peak pricing programs that encourage reduced consumption, facilities with thermal storage have a distinct advantage.

To help customers maximize these opportunities, energy providers offer specialized tools and alerts. For example, our customers can sign up for Coincident Peak (CP) notifications: 1CP, 4CP, or 5CP, depending on your location. By receiving advance notice of anticipated peak grid conditions, facilities can strategically deploy their stored ice cooling and implement other load-shifting measures to save thousands of dollars in transmission and distribution utility charges the following year.

Is Ice Storage Right for Your Facility?

Ice storage has been implemented successfully in a wide variety of commercial and industrial settings, including office buildings, universities, hospitals and data centers. The decision to invest in this technology depends on several facility-specific factors.

An ice thermal energy storage system can be an especially effective and cost-efficient long-term investment if your facility experiences significant variations in electricity rates throughout the day. It is also highly beneficial for facilities facing high electricity demand charges. If your average cooling load is significantly less than your peak afternoon cooling load, an ice battery can seamlessly bridge that gap. Furthermore, if your facility is expanding and requires additional cooling capacity or if your existing cooling system needs extensive repair or replacement, integrating partial ice storage can reduce the capital expense of buying oversized traditional chillers.

Managing energy effectively requires forward-thinking solutions that balance operational needs with budget predictability. By understanding how ice thermal energy storage systems work and how they support comprehensive peak demand management, businesses can take control of their energy profile, support broader grid reliability and achieve meaningful, long-term savings.