Energy efficiencies of instant water provision

Issues relevant to today’s society, such as environment preservation, energy conservation and health care - as well as demand for lower NOx emissions and more efficient use of energy - have led to big advances in combustion and gas control technologies, particularly in instant hot water systems.

Design improvements by leading gas water heater manufacturers have increased heat efficiency of hot-water appliances, from 80% to 95%, while decreasing gas consumption by around 14%.

A continuous flow water heater system is the best option for all applications - from all types of domestic dwelling through to office buildings, hotels and leisure parks and caravan sites. With a continuous flow water heater you can never run out of hot water, no matter how many individual baths or showers are taken simultaneously. What is the point of wasting energy and money heating water for a number of hours for a brief period of use? 


With a continuous flow system the only time you are using energy is when there is a demand, in other words it is only burning gas when a tap or shower is turned on for use.

Conversely, stored hot water has to be kept at 60°C to combat Legionella and other waterborne diseases which add costs because you are permanently heating that volume of water to maintain that temperature. Even if you do not use any hot water, a standard cylinder will lose a maximum of 3kW of heat a day as a standing loss. All cylinders suffer from this to some extent and it actually equates, over a year, to 1095kW of energy wasted; a big hole in the pocket for the benefit of having a cylinder taking up space. If you also look at the gas saving alone it equates to 101.8m³ of gas used.

Another downside to a stored water system is that room has to be found for a cylinder and considerable care would have to be taken when mounting it: for example, when full a standard one could weigh 250kg and be 579mmW x 1486mmH. On the other hand, with an instant system the water heater is wall mounted and is typically only 582mmH x 355mmW x 234.5mmD and weighs just 24kg, so no floor space is lost.


The use of single internal continuous flow gas water heaters can really make a difference to running costs, but step up to a condensing system with a secondary steel heat exchanger within the unit and this is where the very high efficiency figures kick in. The other advantage of a condensing unit is that there is a higher modulation range as these units will modulate down from 59.5kW input to as low as 2.83kW input.

The condensing process can deliver up to 95% thermal efficiency, which translates to significant energy savings when compared to standard tankless water heaters.

A gas continuous flow hot water system is simplicity itself to install as basically it is just three pipes gas in, cold in and hot out. There is no extra specific qualification required as there is with a sealed hot water system engineers do not require G3 unvented cylinders. This means less training and subsequently reduced overheads for the installers.

To make even greater savings, the linking of a renewable energy source to a continuous flow system is very easy to accomplish. The flow of domestic hot water is heated by the renewable energy source and is then fed through the water heater; the idea being that the water unit is pre-set to a temperature of 60/65°C then if the renewable energy source does not get to this temperature the water heater makes it up. The reason for the high temperature is to get the most from the renewable source.


With regards to maintenance this, as all gas appliances, is required once a year and would take on average less than one hour to complete.


For energy efficient plumbing supplies check out Energy Smart.