A cylinder stores hot water ready for use. A DIRECT cylinder heats the water using the electrical elements within the cylinder itself, whereas an INDIRECT cylinder stores water heated by another heat source (most commonly, a gas boiler). Read this article in the Advice Centre for more information. Usually, these cylinders are fed directly from the mains, and so run at mains pressure, and can therefore be sited anywhere in the house. They range in size from 60 litres up to over 600 litres – much above that and you will need a commercial grade cylinder.
Also called ‘Tankless’ water heaters (particular in the USA), these are small units which store no water, but heat it at the moment you turn on the hot tap. They are therefore both very compact, and efficient to run, since you only heat the water you need. They sound ideal, and in many situations they are exactly that, but there are several factors to consider before deciding one is right for you. Have a browse through this article and this one to check how it fits in your particular situation.
Ranging from a small 5 litre unit which sits under a basin, to a 90 litre wall-hung water heater which could service a small apartment, there is a very wide range on this type of heaters available to suit everyone’s pocket. Running at mains pressure, they will usually also require an expansion vessel (supplied with every heater of 30 litres or more, and available as an option on all smaller heaters) to cope with the water expansion during operation heating. This will be the case unless they are described as a ‘vented’ water heater – read about the difference in this article. https://electricaldealsdirect.co.uk/advicecentre/do-i-need-a-vented-tap-with-my-vented-water-heater.html
Boilers heat water for hot water and/or central heating, and are either powered by gas or electricity. Electric central heating boilers can be very compact, and are also called ‘flow’ boilers, as they heat the water as the water flows through them. In this cateogry you will also find 'combi boilers' which cater for both the hot water and the central heating and although gas combi boilers do not store any water, most (but not all) electric combi boilers do have some level of water storage because they are not as powerful as their gas counterparts.
By using the various articles and guides available online you may quickly arrive at the right choice of the water heater you need, but should you need to talk any aspect of your requirement through, we are always happy to discuss your needs and make a recommendation: just call one of our experts on 01934 253600.