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How to Choose a Water Heater – A Complete Guide for Every Household

A photo of a woman choosing a hot water heater

The water heater in your home has a significant role in your everyday life. Everything from simple chores to a hot shower after a long day depends on it. That is why it is vital to choose the model that won’t cause troubles for years to come.

To help you select the best model for your needs, we have prepared this guide on how to choose a water heater. It is useful not only for experienced homeowners but also for those who are purchasing a new water heater for the first time. 

What is a Water Heater and How Does it Work?

As simple as it sounds, a water heater’s job is to warm up your domestic water. Whenever you want to take a hot shower, or maybe do your laundry, this simple-looking machine supplies cold water from the mains and heats it. Let’s not forget that you also use this water for cooking and cleaning purposes. It’s important to mention that in the UK, any water unit that receives water from the public mains should comply with the water supply regulations.

On the outside, this cylindrical appliance looks ordinary, but the insides are complex for someone with lack of experience. Each water heater includes a heating element, powered by fuel or electricity. Depending on the model, the type of fuel can vary. Before getting to the model and types of fuel, let’s discuss the difference between a water heater and a boiler.

The Difference Between Boilers and Water Heaters

Now that we know how a water heater works, it is time to define how water heater and a boiler differ from each other:

  • Electric water heater – The working process of an electric water heater is essentially based on the heating the water with electric immersion heater that is in direct contact with the water. This way the energy loses are minimal, so the boiler is more energy efficient.
    There are a wide variety of electrical hot water boilers to choose from based on your needs and storage space, as some requires a water tank.
    – Electric flow boiler
    – Electric CPSU Boiler
    – Dry Core Storage Electric Boiler
    – Solar Compatible Electric Boiler
  • Gas boiler system – Gas boilers can be connected directly to the gas mains and get a continuous supply of fuel, or they can work with LPG cylinders that you have to refill in a centime time frame. The process is simple – The gas enters the sealed combustion chamber helped by a valve. Then an electric ignition system or permanent pilot ignites to burn the fuel. As the gas is heated, it begins to rise and reaches the heat exchanger, where it’s pushed through the coiled pipe. The pipe is surrounded by cold water, so when the hot gas moves through the pipe, the heat is transferred to the water. Finally, the hot water is delivered to the taps and radiators y the help of a pump.

There are three main types:
– Combi
– Regular / Conventional
– System

5 Things to Consider Before You Buy a Water Heater

Size and Capacity

When sizing your water heater, you should consider the type and technology your water heater uses. To choose the proper size for an on-demand water heater, you need to know the number of appliances and taps that can use hot water simultaneously. To that, consider the maximum flow rate of your appliances and the temperature rise. 

It is not a secret that the bigger the family, the higher the hot water consumption. That is why you need to have a water heater that can store enough water for your household. Here are some recommendations in terms of water heater capacity:

  • One bedroom – between 120 and 150 litres
  • Two bedrooms – between 150 and 180 litres
  • Three bedrooms – between 180 and 210 litres
  • Four bedrooms – between 210 and 300 litres
  • Five or more bedrooms – 300 and more litres

Flow rates are usually presented in the manufacturers’ manuals and counted in litres per minute. Sum the flow rates of your appliances, and you will find an estimated maximum of a flow rate needed for your household. 

Temperature rise is a difference between the desired water and the incoming water temperatures. For most domestic appliances, the desired temperature is around 49 ℃. On average, the incoming water temperature in the UK is equal to 10℃. Therefore, you need to have a water heater that can produce a temperature rise of at least 39 ℃. The higher the temperature level, the bigger the size of the water heater. 

To correctly identify the needed size of a water heater with a storage tank, you need to think of what time of the day you and your family use hot water the most. Consider what is the maximum amount of water you use in that hour.

On average, one minute of a shower is equal to 12 litres, a single dishwasher program uses approximately 10 litres, and a load of laundry needs 60-70 litres per single wash. Compare your results to the water heater’s first-hour rating, that you can find in the manufacturer’s instructions. Search for the models that match your peak hour demand within 3 to 6 litres. 


The diversity of water heaters on the market is represented not only by their size but also by the type of fuel that they run on. Depending on the model, water heaters can operate on gas, oil, liquid petroleum gas or electricity.

Gas water heaters are typically cheaper to have than the electric ones, but you will need to book a gas safe certificate check now and then. 


The efficiency of a water heater explains how much fuel a device actually burns. It is based on the amount of hot water produced per unit of fuel consumed over a day. All modern units have to follow common efficiency ratings approved by the government.

Power and outages

If a power outage happens, the electric units shut down immediately. Unless you have some hot water stored, you will not have access to hot water until the power gets restored. An alternative solution can be to connect your water heater to a backup power supply. 

Gas water heaters are not dependent on electricity. The coil or flame is powered by gas, which allows them to work during a power outage.


Installation of any heating appliance is a major investment and usually includes a lot of variables. The price of a water heater unit depends on the brand, the type and size.

Another essential thing to consider is the price of fuel that runs your appliance. If you compare the fuel types available in your region, you might discover that in the long run, some are more economical than the other. That aside, think about the installation costs or any additional building work to fit a water heater. 

The Types of Water Heaters

Now that you know what to pay attention to, it is time to choose the type of water heater. You might be wondering what is the difference between the specific kinds of water heaters, and how to choose the one that suits your home best. Here is what you need to know about the various options:

Tanked water heater

This type of water heater is a popular choice on the market. The heater takes the cold water from the mains and heats it to the desired temperature. Depending on the fuel your heater uses – gas or electricity – this device warms water with the help of a gas burner or electric heating rods located inside.

As you turn on your tap, the pressure pushes down the hot water from the tank, which allows you to take a nice, warm bath or shower. 

Tankless water heater

As you can guess, this type of heater doesn’t store the water in a tank. It delivers it directly to the tap. The most significant advantage of a tankless water heater is an unlimited supply of hot water. So, when you turn on your tap to do the dishes, the water flow triggers a heat exchanger that transfers heat from a heating device to the water.

Depending on your fuel type, the heating device could be a gas-fired burner or electric coils. The water circulation through the activated exchanger allows you to use hot water anytime. 

Heat pump

Compared to the previous models we’ve discussed, the heat pump models do not generate heat directly. Instead, they use electricity to move heat from one location to another. The heat pump of the water heater pulls the surrounding air, absorbs the heat through a refrigerant and passes it to a tank.

In order for this device to be efficient, the air around the unit should remain in the 5 – 32 ℃ range. Since this water heater uses the surrounding air, the air space should be at least 1000 cubic feet, which makes it a difficult solution for smaller properties. 


This is the most cost-effective type of water heater. It comprises solar collectors and a storage tank. The solar collectors absorb the heat, transfer it through the tubes to the heat exchanger in the heating tank.

Solar-powered water heaters often require a backup system, so you can have warm water when sunlight is not available. You can always combine it with a tanked or tankless water heater system as a backup solution.

Condensing water heater

A high-efficiency water heater model. The unit produces a hot vapour that is further passed through a heat exchanger. It then transfers the heat to the water, thus raising its temperature.

Types of Fuel Sources

  • Electricity – This type of fuel is widely available across the country. It is suitable for the majority of water heater models available on the market; 
  • Fuel oil – Oil is suitable for powering conventional storage water heaters and indirect combination water and space heating systems. It’s significantly more expensive and less common.  
  • Natural gas – The second most popular fuel type that water heaters operate on. It is quite available across the UK, however, all the appliances that use natural gas as a power source should follow installation regulations. 
  • LPG – This sort of fuel is used in tanked or tankless water heating systems. The LPG water heater’s process is like that of a gas model’s, the difference is that it takes the fuel from the separate cylinders. LPG water heaters also have some specific installation regulations.
  • Geothermal energy – If you already have a ground loop system installed, then you might find that this fuel is ideal for your household. 
  • Solar energy – As the name suggests, your unit uses sunlight to operate. There is a myth that solar panels are most effective when powered by direct sunlight, in truth, all they need is some daylight.

6 Modern Features of Water Heaters

  • Anti-scale – Some manufacturers install anti-scale systems in their water heater models. Their purpose is to prevent your device from mineral scale and hard buildup by swirling the water, therefore prolonging the life of your appliance. 
  • Energy efficiency – Energy efficiency class is shown on the energy labels each device has. The classification starts from G (least efficient) and A++ (most efficient). To reach an A+++ efficiency rating, you can install solar panels.
  • Dry-fire protection – Some models have systems that sense if there is no water around. A dry fire protection system prevents the electric flow to the heating elements until the tank fills up to the required water level.
  • Electronic gas valves – Newer models of water heaters can feature electronic gas valves that automatically control the amount of gas sent to the pilot. This modern feature allows your device to work more efficiently and spend less fuel. 
  • Intuitive technology – This feature allows your water heater to adjust to your personal preferences and use patterns, resulting in better efficiency.  
  • Wireless control – The idea behind it lies in the wireless connections between your water heater and a smart device through Wi-Fi or 5G signals. As long as you have your smartphone and a stable connection, you can interact with your unit. The biggest advantages this technology offers are the comfort of control and energy-efficiency.

Common Water Heater Problems to Watch Out For

  • Too little or no hot water at all can signify problems with the pilot light or a faulty thermocouple;
  • Smelly water. Can result from bacteria infestation. To keep the water clean and bacteria-free, the water temperature should always remain between 55-60 ℃;
  • Noisy water tank. Can result from burning sediment on the bottom of your water heater. Another common problem might be a damaged heating element;
  • Leakage. Unfortunately, once you see your appliance leaking, you need to plan a visit from a Gas Safe Registered engineer. Act as soon as you see signs of a leaking tank;

How Much Does it Cost to Install a Water Heater?

The water heater installation cost depends on several factors: the type of water heater, time of the service and additional materials – if required. 

The service is usually charged hourly and on the average, the work takes from 1 to 2 hours, without the additional pipework. So, in general, a water heater installation costs around £220. However, if you are a member of Fantastic Club, you can enjoy some neat discounts on any service. Join the Fantastic Club and enjoy the member-only perks for an entire year!

Key Takeaways

  • Choose a water heater according to your needs; otherwise, you risk having to pay larger bills;
  • Go for the models with the highest efficiency;
  • Gas is the cheapest fuel compared to the LPG and oil fuel;
  • We recommend contacting trained specialists if you have problems with your water tank. Water heaters are complex and can be dangerous if repaired improperly.

How to Choose a Water Heater – A Complete Guide for Every Household

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