What’s the difference between a thermal store and an unvented cylinder?

Although they look similar, a thermal store and an unvented hot water cylinder work in very different ways. An unvented cylinder stores the hot water that comes out of your taps. It's connected directly to the mains water supply, so it delivers high-pressure hot water to your showers and taps. Because it stores potable (drinking) water under pressure, it must be fitted with safety devices and installed and serviced by a G3-qualified engineer. A thermal store doesn't store your domestic hot water. Instead, it stores water that is used as a heat source. When you turn on a hot tap, cold mains water passes through a heat exchanger inside the thermal store and is heated instantly before it reaches the tap. This means the water you use is always fresh and isn't stored in the cylinder. Thermal stores are often recommended because they can: Work with multiple heat sources, such as boilers, heat pumps, wood burners and solar thermal systems. Supply large volumes of hot water very quickly. Reduce the risk of Legionella because the domestic hot water isn't stored. However, they are usually more expensive than unvented cylinders to buy because no of the major manufacturers make them. They could also contain more components, such as pumps, controls and heat exchangers, which can make them more complex to maintain. For many homes, an unvented cylinder is the simpler and more cost-effective option. A thermal store is normally chosen when there is a specific reason, such as: In Flats: The builders did not install a thermal discharge pipe, and the building managers will not let you install one In Houses: You have several different heat sources that need to work together. Your heating system has been designed around a thermal store. You need a very high hot water demand, for example in a large property with multiple bathrooms in use at the same time. If you've simply been told that you "need" a thermal store because you're replacing an old cylinder, it's worth asking why. In many cases, a modern unvented cylinder can provide excellent hot water performance at a significantly lower cost. There are, however, situations where a thermal store really is the best solution or in blocks of flats, the only reasonable solution. That is until electric combination boilers have advanced sufficiently to be cost effective and workable with a standard 230V 100A supply. Visit this page for further information: https://easyflow.co.uk/articles/unvented-cylinders-vs-thermal-store-water-heaters-how-your-options-stack-up