Zip CEX Instantaneous Water HeatingInstantaneous water heaters (also often called ‘tankless water heaters’, especially in the USA)  are becoming more and more popular as people realise their advantages. But before installing them, you need to make sure they are right in your particular situation.

Modern, efficient and compact, this type of electric water heaters have a number of very significant advantages:

Limitless Supply. With an instantaneous electric water heater, you’ll never run out of hot water.

Energy saving.  An electric boiler with a water storage tank loses heat all the time (check out the ‘Standing heat loss’ figures for any particular model), whereas an instantaneous heater does not store any water.

Space Saving. Because they do not store any water, they are extremely small compared to a traditional water heater.  In flats and smaller houses, this can be a real advantage – with no need for a ‘boiler cupboard’, they are small enough to fit underneath a sink or bath.

Reduced plumbing installation costs. In a situation such as a new utility room, running a hot water supply from a central boiler to the new sink is not necessary if you are creating the hot water locally with an instantaneous heater.

Energy, Water and Time saving. Instantaneous heaters are always situated close to the outlet(s) they are serving, and so there is no great wait for hot water whilst you run off several metres of pipework full of cold water. That length of pipe, between a central boiler and the tap, has to be emptied each time the tap is used, and a typical run of 10m of 15mm pipework contains over 3 litres of water: water which usually just goes down the drain and which must be replaced each time, so there is a great deal of wasted water and heating power with a central boiler.

But there are a few limitations of instantaneous heaters which might mean they are not suitable for particular situations:

Special wiring requirements.

All but the smallest instantaneous water heaters will NOT run on a standard household ring main – they will need a special cable run from your fusebox  (just like an electric shower or a cooker). Often, this is not a problem but if this is not feasible then you won’t be able to install an instantaneous heater.

Zip Tankless water heater


Distance is a killer for instantaneous heating. Your heater will work best when it is as close as possible to the outlet it is serving, and if you need to place it more than 2 metres away then performance will start to suffer.  If this does not suit your situation, you can always use more than one instantaneous heater, each one serving an outlet close by.

Flow rate

Expectations can be high of instantaneous water heating, but it is important to understand whether the flow rate you will be able to achieve will leave you disappointed. This is particularly important if you are hoping to fill a bath with an instantaneous heater: consider the fact that an average bath is 80 litres of water, so if you have a flow rate of 3 litres per minute at a temperature hot enough for your bath, then it will take close to 30 minutes to run a bath.


So if you’re OK with the cabling, distance and flow rate issues, then an instantaneous water will be a fantastic choice: read our other blog posts to work out which model is right for you, or call us on 01934 253600.