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Hot water cylinders are a hidden lifeline for energy storage, report finds

As energy security continues to be a cause for concern for the UK, an industry report has identified the potential role of hot water cylinders in balancing demand on the electrical grid.

The report from the Hot Water Association (HWA), entitled Connected Homes, explores the potential for hot water cylinders to be used as thermal stores for grid electricity to build resilience in peak periods.

If the nine million cylinders in UK homes were connected through smart controls and used as batteries, the National Grid could unlock 23GWh of energy storage – around half the energy used per day in the UK. 

Due to the introduction of technologies, like heat pumps, which require hot water cylinders, this number could increase by 36%, increasing the energy capacity to 40GWh.

To make use of this energy storage potential, cylinders will need smart functionalities introduced either via retrofitting smart controls or brand-new smart cylinders will need to be installed with gas boilers or heat pumps.

Heating engineers will be key in the process of making this a reality, as Kevin Lowe, Technical Manager at the HWA, said: “Hot water cylinders’ potential role in the energy mix is substantial and there is work to be done to make the most of this opportunity. Installers across the UK installing and maintaining cylinders in homes can play a crucial part in this, as our report highlights, by making existing and new cylinders connected.”

The report from the HWA also highlights the need for policy direction to incentivise the rollout of connected thermal storage in UK homes for homeowners. This is particularly needed to prevent people from changing their hot water system to remove the cylinder completely so the number of cylinders in the UK can increase to build capacity.

In addition to incentives to drive more people to install smart cylinders and retrofit controls to existing cylinders, the report lays out next steps for improving uptake. This includes making smart controls and cylinders more beneficial to SAP and EPC ratings in new builds and reducing taxes and levies on off peak electricity to bring more value out of storing energy in a cylinder.  

Kevin continues: “The key to making this project a reality will be getting homeowners on side, so policy direction must incentivise adopting smart hot water storage. Whether installing a cylinder with a new heat pump installation, or fitting controls to an existing one, homeowners may require financial support to make it worth their while. They will also need to understand the benefits that thermal storage in their home may provide and in turn prevent them removing an existing hot water cylinder.

“If we are to get the up to 40GWh of energy storage that our research predicts could be achievable in the UK, industry, Government and installers must work together to help homeowners understand these benefits.”

To download the report and find out more about your role in the rollout of thermal storage in the UK, click here.


6 December 2023


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