Gas Water Heaters

Gas Water Heaters

gas water heaters energy efficient hot water heating from Flexiheat UK

Gas Water Heaters

A gas water heater or gas fired water heater is used to produce domestic hot water for your domestic properties e.g. flat, house or commercial property. This hot water is of sanitary quality and is used to feed showers, baths, and hot water taps or faucets. They can be mains gas (natural gas) or LPG gas fired.

Water heater gas fired

One of the many benefits of a gas water heater is the energy delivery that it can dissipate into the water and thus the good flow rates they can achieve when compared to instantaneous electric water heaters, which require a lot of Amps for heating water and normally a three-phase electric supply to achieve similar flow rates.

Gas fired water heaters

Our entire range of our gas water heaters can be powered by either mains gas (also known as natural gas) or LPG (propane gas), which is your liquid gas. It is easy to convert our high energy efficiency gas fired water heaters from one type of gas to another via a simple-to-fit gas conversion kit.

Hot Water Heaters

Gas fired water heaters can be split into two main categories:

On demand water heaters

On-demand, tankless water heaters or instantaneous water heaters will use less energy than storage water heaters and are the most energy-efficient method for heating water, with high performance mains pressure to all warm water outlets. However, the instant hot water flow rate demand and the usage of the hot water outlets by the customer installation must be considered to ensure they’ll work correctly. These gas water heaters are low NOx and cost effective and available in natural gas or LPG. We go into more depth on this range here – instantaneous gas water heater

Storage hot water heaters

Alternatively, we do a range of low NOx storage gas water heaters, which are condensing water heaters with high energy efficiency; the two stock units have a water storage quantity of 150 litres, which is ideal for customers with a larger demand for domestic hot water, such as having a periodic requirement for high volumes of water in a short period of time or intermittent times, that an instant hot water heater couldn’t service with its flow rates. You simply need to store water / storage systems for certain customers’ requirements in the most cost effective manner.

Storage gas fired water heaters with an inbuilt 150 lire stainless steel hot water tank energy efficient hot water heater from Flexiheat UK

Storage option – 28kW or 34KW output options

The “SFKA” range, as they are designated, is available in natural mains gas or as LPG as their fuel source and is available with an output of either 28kW or alternatively a 34kw output model.

They come complete with a 150 litre stainless steel storage tank, which has a long warranty, and all the associated plumbing pipework and a pump local within the casing.

internal picture of our hot water heater with storage tank which is gas fired from Flexiheat UK

SFKA 28 or 34 KW Output models – Natural gas or LPG powered

They also have easy access for service or to maintain this reliable water heater unit as the panels are removable-with loads of room to get at and checkout the plumbing components that connect the heat exchanger of the gas water heater to the storage tank. These gas water heaters are sometimes referred to as a gas hot water tank or cylinder, and are detailed on this webpage – gas hot water tank or cylinder  in full detail.

Thermal efficiency

In any domestic or commercial hot water heating system, any gas fired water heaters used these days must not only be a reliable appliance but also as efficient as possible.

This is where condensing water heaters come in as a solution with regards to gas fired water heaters, as you can recover the latent heat from the heater’s flue gases and recover that energy via a heat exchanger back into the hot water temperature-and not lost to the flue gases and the environment whilst saving the customer money.

Gas fired water heaters in condensing mode as it extracts all the energy from the fuel

Gas fired water heaters – Because the flue gases leaving the water heater are cool, they form a visible mist or plume of water vapour whilst leaving the flue terminal point or location


Because of this condensing process, our condensing gas water heater range are at least 15% to 20% more efficient than non-condensing systems. With the current high cost of energy, any customer may save significantly on their water heating costs by the installation of a water heater that will condense, whether in a domestic or commercial application.

ErP A rated gas fired hot water heaters - contact Flexiheat - picture shows energy efficiency sign so the customer can make an informed decision

Thermal efficiency or energy efficient ErP rating – “A”


This type of water heater is ErP “A” rated-and due to recent legislation changes, you must now fit condensing gas fired water heaters in all new and retrofit commercial water heating systems. Please visit this location on our site for more in-depth information on this- Water heater legislation changes-Part L Building Regulations-June 2022

Gas water heater controls

You can use the thermostat built into the control panel on the gas water heater to set the hot water temperature output required, or alternatively, we do a remote temperature controller option too.

If you require any more suitable support, solution advice, check stock, delivery times or require a price on our gas water heaters from Flexiheat UK, then please use the contact us form page on the website, or alternatively feel free to give us a call on 01202 822221, as we sell direct to the trade and public customer base. Connect with us on Facebook or Twitter so you can contact us at any time.