To practically achieve full decarbonisation in the energy transition, there is a need for affordable energy storage solutions to balance demand with supply from intermittent renewable energy sources, and so replace fossil fuels. One accessible method of energy storage is to store surplus supply as heat, which can then be used in domestic or municipal heating and hot water applications. It has recently been recognised that hot water cylinders are a core feature of many existing decarbonisation strategies and can be used for thermal energy storage [No Place Like Home: Cylinder Batteries – Tapping into the Potential of Hot Water Storage,Hot Water Association (2022). Available at 6177D216E375E.pdf].   ShowerPowerBooster Ltd have patented a technology [GB2623198] to use existing hot water systems for thermal energy storage with minimal modification. This allows replacement of 100% of the heat load from gas with 100% renewable energy. This can be applied in individual homes, hotels, public buildings, and factories, with a particular focus on replacing gas boilers or improving the efficiency of Heat Pumps (HP). The principal advantages of this technology is the rapid and low-cost upgrade of any existing heating system, without needing to replace the hot water system.   ShowerPowerBooster Ltd is currently selling a commercialised product which benefits from independent validation of the technology. This allowed us to optimise the design and operation parameters. Computational fluid dynamics (CFD) simulations of the device, in operation in a domestic setting, have demonstrated that x4 more energy can be stores in a simple tank than previously predicted. When compared with complex tanks which claim to be market leaders, it stores twice the energy (x2), at half the cost. These simulations prove an almost perfect thermal stratification (thermocline) can be maintained in the hot water cylinder while also acting as a heat store and is a “game changer”. Market Application This technology addresses the pressing need for residential heat storage solutions that work across the full spectrum of UK households. It is equally effective for properties with combi boilers (80% of the market) and those with conventional heating systems, offering a clear path to mass-market deployment. The system enables complete flexibility in heating load management, supporting the transition to a renewable-powered grid while reducing energy costs for consumers.   Benefits To Customers Storage of low-cost off-peak energy or surplus renewable energy at the flick of a switch. Replacing up to 100% of gas use in a home without replacing the water tank. Shift reliance on fossil fuels to surplus renewable electricity at a lower cost compared to heat pumps.   Benefits To The UK Government Achieving grid balance without building more gas power stations or major upgrades to the UK National Grid but simply repurposing existing water tanks.   Enabling Mass-Market Thermal Storage for Grid Flexibility This is a fundamental advance in thermal storage efficiency that addresses a critical challenge in grid decarbonisation. By enabling practical, cost-effective residential heat storage at scale, this technology opens new possibilities for grid balancing and renewable energy integration, creating a clear pathway to widespread adoption.   Technical Innovation At the core of this opportunity is a patented approach to thermal stratification control. The technology maintains separation between stored and incoming water in both space heating and hot water systems, significantly improving storage efficiency and enabling practical deployment at scale.  Gateway Technology. At the heart of this technology is the ability to create perfect showers and water flows without complexity and cost leading to Energy Saving, Water Saving, balancing Electricity and Water Networks and increasing Electricity and Water Supply making this the only technology that can allow homes to be built in areas of scarce water and power.