Updated on 10th May, 2023 by Martin Astley

Living in the UK, you may have heard of immersion heaters, especially if you have a regular or system boiler. Immersion heaters are electric water heating devices that heat the water in your hot water storage tank, providing a reliable and efficient source of hot water.

Although immersion heaters are not as popular as combi boilers today, they can still be incredibly beneficial for those with an old boiler or an interrupted gas network. This article will explore what an immersion heater is, its advantages, how it works, and much more. So, let’s dive in!

How does an immersion heater work?

How Immersion Heaters Work: Explained in a Diagram

A residential immersion heater is an electrical heating device to heat pre-filled water tanks. It converts the electric current into heat that dissipates through the surrounding medium, usually a particular fluid in a sealed container such as a tank. The heated fluid transfers its thermal energy to the water, raising its temperature. It is important to note that immersion heaters cannot work without an electric current source, which means they will not operate when the electricity supply is lost or disrupted.

Additionally, if an immersion heater contains multiple elements, it may be necessary for an individual component to be activated before producing sufficient heat to raise the water temperature. Moreover, it is essential to ensure that any exposed wiring is safe and grounded correctly to prevent potential electric shock risks. Overall, residential immersion heaters provide reliable and economical hot water supply on demand when installed and maintained correctly.

Is there any particular way to use an immersion heater?

Using an immersion water heater can reduce maintenance costs and ensure safety when heating water. First, it should be adequately insulated. Then it should be filled with the water to be heated, then submerged in the container near—but not touching—the container’s walls. A thermometer should be used to test the temperature of the container before and after inserting the heater to verify that it is adequately insulated from other surfaces, as heating happens quickly.

To prevent power overloads and potential electric shocks, users should always ensure that the wattage rating on their appliance matches or exceeds that of the electrical outlet and monitor circuit breakers located at the immersion heater fuse box to ensure proper functioning.

Additionally, all insulation around hoses and cords should be applied following manufacturer recommendations for this product’s safe and secure use. It is highly recommended to install a thermostat to ensure your immersion heater runs at an optimal temperature.

For hard water areas, the ideal temperature should be set at 50 °C. In the case of the twin immersion heater, the top element should be set to a rating of approximately 49°C to 50°C, and the lower one to approx 59°C to 60°C. In soft water areas, both single and twin immersion heaters should be set to 60°C for maximum efficiency.

Advantages of an immersion heater

Immersion heaters are a great way to ensure you always have hot water, even if your boiler breaks down.

They are also compatible with solar panels, allowing you to heat water with renewable energy and save on electricity costs.

Insulated tanks help immersion heaters keep the water hot for several hours and are easy to operate.

Installing a thermostat with an immersion heater further increases its efficiency. It will automatically turn off when the water reaches the desired temperature and switch back on when it cools too much.

Immersion heaters are ideal for homes not connected to a gas network.

Disadvantages of an immersion heater

Immersion heaters use electricity to heat water, but their main disadvantage is that they cannot heat small amounts of water, which makes heating a tank of water lengthy. It typically takes an immersion heater 2–3 hours to heat the water, making it time-consuming.

Furthermore, when the immersion heater is turned off, the water quickly loses its heat, resulting in energy waste if the water is not used up.

Installing a thermostat can increase the heater’s efficiency, but without one, a significant amount of energy will likely be wasted.

Types of Immersion Heaters

1- Over-the-side Immersion Heaters

Over-the-side immersion heaters are specially designed for vessels where submersible heaters cannot be installed. These heaters are installed through the top of the vessel, with the heated portion facing the side or bottom, providing an ideal solution for vessels where submersible heaters are not an option.

Not only are over-the-side heaters easy to remove, but they also offer ample working space in the tank. This makes them an ideal choice for applications where submersible heaters are not feasible.

2- Threaded or Screw Plug Immersion Heaters

Screw plug heaters, also known as threaded heaters, are designed to be directly screwed into the wall of a tank through a threaded opening. These immersion heaters are ideal for freeze protection and process water heating applications. They provide a reliable and efficient way to maintain the desired temperature of a liquid.

3- Flanged Immersion Heaters

Flanged immersion heaters are designed for tanks and pressurised vessels, making them one of the most widely used methods for heating gases and liquids. Installation and maintenance are simple, as these heaters are bent into the shape of a hairpin and then welded into a flange. When you begin to install, the heater is attached to the corresponding flange welded to the side of the tank, providing a secure and reliable connection.

How much does an immersion heater cost to run?

When discussing the cost of an immersion heater, there are several factors to consider. As previously mentioned, there are various types of immersion heaters, and when shopping for one, you will need to select from a range of materials. The available materials for an immersion heater include:

Material	Cost	Installation Cost
Copper Immersion Heater	£14-  £20	£105- £120
Incoloy Immersion Heater	£17-  £30	£106- £130
Titanium Immersion Heater	£25-  £120	£115- £220

Additional Cost:

When purchasing or replacing an immersion heater, there are certain additional costs that you may need to bear. These costs include labor, a thermostat, and radiators. The cost of a thermostat can range from £110 to £400, as there are multiple options, such as manual, smart, and programmable thermostats. After investing in a thermostat, you may need to invest in radiators.

Old radiators can reduce your heating potential, wasting energy and money. The replacement cost of radiators can range from £110 to £450. This figure will depend on the number of radiators that need to be replaced. In addition to the optional thermostat and radiator costs, you will also need to pay for labour, which ranges from £80 to £120. If the engineer needs to travel to your location, which is out of their region, to install the immersion heater, they may charge an additional fee of £40 to £80 per hour.

Conclusion: Buy or not to buy?

After reading this far, you know that immersion heaters are electric water heaters that connect to the electric mains via a cable and can heat water on demand with the flick of a switch. Whether or not to invest in one depends on your situation; if you have an old system or a regular boiler, then an immersion heater could be a great help, but for the long-term, it is advised to invest in a more efficient combi boiler.

An immersion heater is an excellent device for backup hot water and can also be helpful if you are not connected to a gas network. However, relying too heavily on an immersion heater can be costly, as it requires a lot of energy to work to its full potential.

Suppose you want to get a new boiler to replace an old one. Contact 24|7 Home Rescue. We can help you get an efficient boiler that will save you a lot of money on energy bills. And if you are finding it expensive to buy a new boiler, we may also be able to help you get an A-rated boiler on finance.

FAQ’s

How long does an immersion heater take to heat up?

Immersion heaters are a reliable and efficient way to heat water, with the time it takes to warm up varying depending on several factors. The size and power of the immersion heater, as well as the temperature of the starting water, are critical determinants of how long it will take to heat up. Generally, using an immersion heater will take 2–3 hours to heat up your water, so it is important to remember that this is time-consuming.

What is the lifespan of an immersion heater?

The lifespan of an immersion heater depends on its usage but generally ranges between two and three years. This time can vary depending on the frequency of use. If used as a backup option, the lifespan may exceed three years, whereas if it is heavily relied upon to heat water, the lifespan may be less than two years.

How often should an immersion heater be serviced?

Immersion heaters should be serviced annually to ensure they are in top working condition. The heater must be inspected for any corrosion or blockages, and the electrical connections should all be checked for signs of damage or wear. In addition, internal components such as heating elements, thermostats, and temperature controls should also be checked for proper functioning and replaced if necessary.

Through regular inspections and maintenance of immersion heaters, homeowners can rest assured that their heating systems will remain efficient and reliable.

Can the immersion heater be repaired?

Qualified technicians can repair immersion heaters in some cases. To determine if the immersion heater can be cost-effectively repaired, the technician must consider multiple factors, including any existing corrosion, damage to wiring and components, and operational functionality. Depending on what needs repair, the technician may need to replace the thermostat or heating element, depending on the make and model of the heater.

Suppose any repairs are needed that exceed the cost of replacement. In that case, it’s recommended that a replacement be installed, as this will ensure a reliable source of hot water at a lower overall cost.