How can you store more energy, up to 150%, in 27% less space?


In these times of extraordinarily high utility bills, it is essential to store more energy from all available heat sources, including renewables, utilising their full potential and ultimately reducing the running costs of the property.

An energy storage system allows the homeowner to capture heat or electricity when it is readily available, including from a renewable energy system, and storing it for you to use later. The most common energy storage systems include electric batteries, heat batteries and thermal stores.

With a traditional hot water cylinder, whether it is a vented or unvented model, the stored water held in the cylinder is taken up to a maximum of 60 degrees. In energy terms, this would equate to 6.99kW of stored energy in a 300 litre cylinder.

A standard hot water thermal store such as our MULTIflow, allows for this temperature to be raised to 75 degrees, increasing the energy storage potential to 12.24kW, an increase of 75% over its traditional vented or unvented equivalent.

Where heat batteries, which incorporate phase change material, dependent on grade are limited to 75 degrees, using a hot water thermal store that allows the temperature to reach 90 degrees, such as an ELECTRAflow or ELECTRAstore. This increases the storage potential to 150% above the unvented equivalent, with the store being able to hold 17.48kW of energy. In addition, phase change material requires a high temperature input to provide a melting point for the material, whereas a thermal store can utilise low grade heat as low as 40 degrees.

One of the restrictions when utilising hot water cylinders for energy storage is the available space within the property to house the unit. This is seen as an issue especially within a retrofit installation or an apartment where space is of a premium.

This is where the flexibility of rectangular thermal stores come into their own! For example, a 150L cylindrical thermal store with incorporated F&E tank is 1700mm high, but the equivalent volume rectangular thermal store with incorporated F&E tank is only 1303mm high, a saving of nearly 400mm and 24% on the height.

As you can see, where a compromise in unit size is required by the installer, it does not have to mean a reduction in energy storage or performance.

With bespoke design flexibility of our thermal stores, whether cylinders or rectangular tanks, our solution will meet any installation requirement.

Taking all this into account, the unique ability of the thermal store to harness the energy as it is generated, store it until it is required and then transfer the heat into heating and hot water on demand, with simplified installation, makes it the perfect solution for both installers and home owners alike.

The Hot Water Association also highlighted this via social media stating the humble household hot water cylinder can also act as a thermal home #battery, storing excess energy in the form of hot water, as well as supporting the grid during times of lower demand and higher input, read their full report here.


Wayne Hyde

Product and Marketing Manager

Having been in the cylinder industry for nearly 20 years, in both product and marketing roles, I have extensive knowledge of all aspects of hot water storage, from domestic through to commercial applications, including vented, unvented and thermal store solutions.

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