Immersion Heaters: Advantages, Disadvantages & Costs

Homeowners have many options when it comes to heating water on their property. One such reliable method is an immersion heater which of course, employs electricity to provide hot water. While these were wildly popular in yesteryear, combi boilers or renewable heaters seem to be all the rage these days.

That said, there are many potential benefits to having an immersion heater. For one, they are great backup options in the case of unreliable or old boilers. And you can rely on an immersion heater as the primary hot water source, if your home does not have a gas supply.

We will outline the pros, cons, and costs of an immersion heater—basically, all you need to know. Read on to find out if this electric water heater is the most suitable hot water source for you and your family!

What Is An Immersion Heater?

As the name suggests, an immersion heater requires you to insert it into the hot water cylinder. You will find the majority of them use electricity to heat the surrounding water. However, it is not uncommon to connect them to solar panels, which adds to their ecological efficiency.

They come with an electric resistance heater (a metal loop or coil) to heat the contained water. Since a cable connects these heaters to a power supply, you may switch them on and off as you please.

Immersion heaters also go by the names of megaflow boilers or unvented hot water systems. You may want to keep this in mind when searching for electric heaters among the many brands and companies.

Types Of Immersion Heaters

Immersion heaters are available in three standard types. If you are considering purchasing one, you must know about all three to know which is most efficient.

  • Over-the-side Immersion Heater: Typically, you install this water heater type from the hot water cylinder top with the heating element along the side or bottom.
  • Flanged Immersion Heater: The installation of flanged heaters involves attaching it to a corresponding flange welded to a storage tank wall or nozzle.
  • Screw Plug Immersion Heaters: You will find these heaters screwed directly to a tank wall, either through a threaded opening or a matching pipe coupling. A half coupling or welding flange will also do in place of a pipe coupling for this type.

How Does An Immersion Heater Work?

An immersion heater works along the same lines as a large kettle. Typically, you place the electric heater in the hot water cylinder and let it sit there as the surrounding water heats. A strong electric current powers the heater to bring the water to the desired temperature.

When the electric heater is on, it will automatically heat water every time it falls below the desired temperature. However, there is also an option to switch off the hot water if you don’t require heating. This feature is especially efficient during peak electricity hours.

The way it works is cold water fills the tank bottom and rises to the top as it gets hotter. The flow of more cold water into the tank bottom creates pressure for the hot water to leave the heater. So it then makes its way to baths, showers, and sinks as needed.

The Benefits

Installation of an immersion heater in your home can be beneficial in more ways than one. After all, they are efficient, cost-effective, and even environment-friendly if you rely on solar powering. So let’s consider the significant advantages they offer.

Backup Your Hot Water Supply

One of the main benefits of an immersion heater is making an excellent backup option to aging boilers.  Since they do not work on a gas supply, you can use these water heaters whenever you have an electricity supply. That means you will have a steady source of hot water even when any central boiler issues arise.

Eliminates The Need For Gas Supply

Some flats and properties, particularly in remote locales, will not connect to the gas supply. For such homeowners, the most viable source for hot water supply would be immersion heaters. After all, these heaters require electricity, and every home has an electric grid.

Control Your Energy Use

Another benefit to having an immersion heater is that it allows easy management of your energy use. After all, you can turn it on and off as necessary because you do not always need hot water.

The best approach is to install a thermostatic control system along with your immersion heater. This control ensures the heater turns itself off as soon as the water reaches the desired temperature. Similarly, it switches the heater on automatically when the water cools too much, which adds to its efficiency.

Lower Upfront Costs

An immersion heater is by far the cheapest water heating solution in terms of initial costs. Factors like type and size will most heavily influence the price of an immersion heater. Besides this, the installation charges will be separate. 

Unlike gas heaters that need additional piping and a new ventilation system, immersion heaters need no home infrastructure adjustments. So the installation process for this hot water source is effortless, fast, and, of course, less expensive.

The Drawbacks

In the 70s and 80s, immersion heaters provided hot water in almost every home around the British Isles. However, over the years, their disadvantages have become more apparent when compared to some modern solutions. Let’s take a look at some of them.

Time-Consuming Process

The biggest problem with an immersion heater is you cannot use it to heat just a small amount of water. Instead, you need to wait for all the water in the tank to heat. 

Besides being a time-consuming process, this also seems relatively inefficient. After all, once you switch the heater off, the water will lose much of its heat. That means all the electricity you spend will go to waste.

Expensive Without A Thermostat

Homeowners who do not have a thermostat try to get around this problem by leaving immersion heaters running. In reality, this is a massive waste of electricity, which is the costliest method to heat water. Installing insulating jackets and thermostat control and timer can work to enhance the heater’s efficiency.

However, they are still among the much pricier systems of heating water.

Buying Or Replacing An Immersion Heater

The price of immersion heaters tends to vary based on their types and sizes. You will find that the least expensive ones are the copper immersion heaters. However, these do not work well with hard water, unvented cylinders, stainless steel tanks, or thermal store units.

If you live in an area of the UK with hard water, Incoloy or titanium immersion heaters will be more suitable for you. Although more expensive than copper ones, they are still reasonably priced. Bear in mind, though, that you will also have to buy a hot water tank and then there’s the price to install it, which can vary greatly across installers.

If you need to replace an immersion heater, ensure that you rely on a qualified engineer. The process can take up to half a day and often involves draining the water storage tank. The draining might be partial or complete depending on whether there is access to the immersion heater or not.

Remember that replacing an immersion heater is expensive as it requires both electricity and plumbing work. So it is advisable to get price quotes from a variety of professional engineers before hiring someone for the process. 

How To Calculate What Size Heater You Need

The size of the immersion heater will also factor into its final price. So it is essential to figure out what size immersion heater you require before making a purchase. To do this, you need to know your tank’s water capacity and the temperature rise required.

With this information, perform a quick calculation to determine the power needed to heat your water tank in one hour. The formula is as follows:

Tank Volume x 4 x Temperature Rise / 3412 = Power (kW) needed

Say your 160-liter tank holds cold water at 20°C, and you want to heat it to 60°C. In this case, you would use the calculation: 160 x 4 x 40 / 3412 = 6.4kW. That means a 6kW immersion heater will heat your tank in a single hour. A 3kW heater, on the other hand, will do the same in two hours.

Immersion Heater Problems

By this point, you know all the basics of an immersion heater and how it works. However, if you’re considering installing this water heater, there is something else to consider: common immersion heater problems. This section will cover such issues and provide solutions to them as well, so read on.

Damaged Immersion Component

Generally, when an immersion heater reaches the end of its lifespan, you will find such issues cropping up. The reason being, rust tends to damage the immersion elements over time. Such problems become apparent the longer you continue to use the heating cylinder.

For instance, you may notice your heater takes ages to provide hot water. Or it may do the opposite and heat the water unexpectedly fast. You may also find your heater turning on and off suddenly due to element damage.

What’s the solution? Fixing an immersion heater’s central components is a pretty tough challenge when it comes down to it. It requires removing the old heating part, cleaning the opening, and installing the new element.

While this may seem like an easy task on the surface, you need prior experience in plumbing. Along with that, at least some understanding of electrical fixtures will be helpful. Without a doubt, this task is far from ideal for a DIY project. Instead, it is best to rely on a professional technician to handle the issue and get your heater working.

Limescale Buildup

Immersion heaters in areas with hard water tend to suffer from excessive limescale buildup. This buildup results in the heater breaking down much quicker than expected. Besides, when this limescale forms around the central heating elements, it can cause other severe issues. In effect, it creates a bottleneck in the whole structure.

What’s the solution? You way to prevent limescale buildup is to fit your immersion heater with a filter to keep out any damaging element. A specialist can best help you with the same. 

Another trick is to disassemble your immersion heater and wash the scale with a high-pressure water stream. This second tip, however, is more suited to someone with expertise. So avoid it if you haven’t done something like this before.

Insulation Problems

An insulation breakdown will entirely disrupt the flow of electric current running through the immersion heater’s heating elements. This disruption causes a system overload that has a detrimental effect on wires and fuses. Not to mention, it can even trip your main circuit breaker.

What’s the solution? The best call is to have a professional analyse your immersion heater’s central heating system and wiring in this scenario. They will be able to guide you about parts that require maintenance or replacement accurately. It is best not to fix an immersion heater’s internal problem yourself for health safety purposes.

Tripped Circuit Breaker

When it seems a cylinder isn’t working or providing hot water, it may be that there is no running electricity. At times, this may happen because a circuit breaker trips down due to overloading.

What is the solution? Check the immersion heater’s circuit breaker in the main breaker panel to ensure it is on. If you find it has tripped, switch it off and on again. Then wait for a bit to see if it trips once more. On the off chance it does, get ready to call a professional because you are facing a more severe problem.

A little word of caution, make sure to switch the breaker off before handling it for your safety. If possible, check that there are no electric currents in the wires with a voltage tester before touching any element.

Immersion Heaters: Good Value In 2021?

Without a doubt, immersion heaters do have their flaws, as do all other water heating systems. That said, having one also comes with positives, more so if your home does not have a gas supply. To put it simply, most of the benefits of an immersion heater depend on how you use them. 

When used correctly, these electric heaters are not only efficient but environment-friendly and can even minimize costs. So whether you invest in an immersion heater as a primary water source or a backup, ensure regular maintenance. Doing so will keep electric heating systems in top-notch condition, so users get the most out of them!

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Last Updated on May 3, 2021

Frequently Asked Questions

Should you keep your immersion heater on all the time?

People seem to think that leaving immersion heaters running reduces costs, but this is far from the truth. Unless you want to pay more, keep the switch off and reheat the water only as needed.

How do you work out what size immersion heater you need?

The size of your immersion heater depends on your tank’s water capacity and the temperature rise. This formula will determine the necessary power for heating: Tank Volume x 4 x Temperature Rise / 3412 = Power (kW) required.


Author: Indra Gupta

Indra is an in-house writer with a love of Newcastle United and all things sustainable.

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