Hot Water Cylinders

Find out more about Hot Water Cylinders.

Connected Hot Water Cylinders

Did you know- The humble household hot water cylinder not only provides you with all your hot water needs, but it 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. This is emerging technology gaining momentum rapidly. Here’s what you need to know:

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Hot Water Cylinders

A standard 150 litre hot water cylinder installed today in the UK can hold ~7kWh with a range of anywhere between 90 litres (4.2kWh) and 300 litres (14kWh).


How a connected cylinder works


The Cylinder capacity is used to provide the hot water needs of the household. The connected cylinder works by having the ability to delay any re-heating requirement to times when there is a surplus of electricity in the grid, electricity that could otherwise be wasted.


Why would the Electricity Grid want excess energy?

From time to time the electricity grid has excess electricity generated through its network. It needs to use this energy or it will be wasted. Some energy companies even pay the customer for using this surplus electricity.


This will become more common with renewable electricity like wind turbines and solar. It needs to use this energy otherwise it will be wasted.


The Thermal solution

With over 10 million hot domestic hot water tanks installed, the UK has 70GWh of untapped energy storage potential. Some energy companies will even pay customers for that excess capacity.


Replacing an old hot water cylinder with a modern, well-insulated one, with smart controls, provides an opportunity to use low cost or even negatively priced electricity alongside the existing heating equipment. They also offer: ease of control, enhanced system boiler efficiency, and future retrofit options for heat-pumps or hydrogen-ready gas boilers.



Solar PV


It’s not just the electricity grid that can benefit from energy storage technology, such as hot water stores.


By combining a solar PV installation with a hot water cylinder homeowners can divert any excess energy generated by the Solar PV system to an immersion heater. This, in turn, heats the hot water cylinder, which may ordinarily be fuelled by a boiler, for use later on. Utilising excess energy n this way will save significantly on gas bills.


Hot water storage cylinders offer great potential to help accommodate more renewable energy sources into the UK’s generation infrastructure as well as supporting the grid by offering excess storage capacity.


Do I need advanced controllers?

In short, yes. Smart thermostats are retrofit items available to convert a new or pre-existing installation to a smart cylinder, this will allow for almost any installation to be upgraded with very little disruption and in some cases without the need to drain a cylinder at all and works completed in under 30 minutes.

When using smart thermostats, you are able to monitor and control the set temperature of the stored water at any time of the day and with an API connection, it is possible to talk directly to the grid and work on a Demand Supply Response supply allowing the grid to take advantage of potential energy storage. 


To find out how a connected cylinder could work for you, contact one of our members today!

Driving to improve standards within the domestic hot water industry