Cylinder options in a changing landscape

The heating and hot water industry landscape is changing rapidly, both for engineers and homeowners. Economic and environmental factors both play a part in this transition towards innovative and alternative, renewable energy generation. Isaac Occhipinti, director of external affairs, the Hot Water Association, HWA, takes a whistle-stop tour around the hot water storage options available in today’s evolving marketplace.

A homeowners brief

I need enough hot water for two adults and three kids. I don’t want to run out of hot water. I want to produce hot water efficiently. What’s the most economical way to produce hot water? I don’t have much space for a hot water tank system. Can I have a hot water tank if I don’t have an airing cupboard?

Does this sound familiar? As heating engineers going into people’s homes daily, you will be well versed with the varying demands from house to house. No two are the same, which is why product choice has become so important, along with energy efficiency and cost.

Specifying the ‘right fit’ requires knowledge; this includes considering the different types of water heaters available and determining the right size and fuel source for a home.

Home connected to the GAS mains

  • Most popular fuel for heating and hot water.
  • Consider storage for properties with more than one bathroom.
  • Storage offers simultaneous multi outlet use if the cold feed pressure is OK.
  • Storage offers faster flow rates; You can run a bath in three or four minutes.
  • Storage can be fitted with existing combi boiler systems, to enhance performance if a property is extended or an en suite shower is added for example.
  • A storage cylinder will provide Hot water even if the boiler is not working.

Home using oil as an energy source

  • Low-carbon biofuels, currently in development, may replace traditional oil heating.
  • Works well with storage and all above points from the gas powered section apply.


  • Increasingly popular due to the advent of heat pumps. Storage for water heating is the only realistic method of generating hot water.
  • Enjoy the comfort and performance of storage.
  • Ability to utilise lower priced off peak electricity tariffs.
  • Can be combined as a thermal store system for heating and hot water.
  • See also solar systems.


  • The perfect marriage of technology and performance as solar PV could provide all of your hot water needs on days when solar gain is sufficient – about half of the year.
  • Storage acts as a battery – storing “free” electrical energy as hot water for use later.
  • If you enjoy the feed in tariff this is a way of getting an extra benefit.
  • In thermal store systems, solar PV can contribute towards the heating load.
  • Low maintenance.


  • Storage is a must to enjoy this system.
  • In a properly designed system, all hot water needs could be met for more than half of the year.
  • Can also contribute towards heating in certain systems.
  • Very low maintenance.


  • Utilising electricity these units produce many times the energy they are fed with – up to 3.5 times as much.
  • Storage has to be utilised for domestic hot water with its associate comfort and performance.
  • Storage can also help to manage heat loads utilising buffer tanks.


  • If a back boiler is fitted to a log burner, for example, it can contribute to water heating and space heating.
  • HWA has developed a specification with HETAS for safe effective utilisation of hot water storage with uncontrolled heat sources.


  • Any of the above can be combined for hot water and central heating utilising storage.
  • Ask your HWA member for information on specific systems.

Other methods of producing energy at a micro scale such as wind turbines, hydro power and so on, can all assist the generation of hot water which can be used for domestic outlets or central heating. Water is the perfect medium for the storage and transmission of heat, and for harvesting renewables and low power output appliances it is an essential part of the mix.

Turning briefly to combi boilers, the HWA recognise their place in the market; providing heating and hot water to approximately 16 million households, they are great ‘in their place’. But it is widely acknowledged that multi outlet use can be, a ‘no go area’ with some combi boilers. Homeowners with demand for simultaneous multiple outlet use have come to realise that combi boilers are not suitable for every property. In addition, most currently available low carbon heating solutions require a hot water cylinder, and this is reflected in cylinder sales year on year.

I hope that this brief guide is of use to you as you go about your daily work. If you have any specific questions about hot water storage, members of HWA are happy to answer them. Member details can be found on our website You will also find a host of useful resources.

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