Immersion heaters offer an electric alternative for heating household water. Because they use electricity instead of gas, they can make use of renewable energy, and nearly all the electricity consumed by the heating element is converted into heat.
However, they can be expensive to run and take time to heat a cylinder of water. Could an immersion heater be suitable for your home, or would another option better meet your needs?
How Do Immersion Heaters Work?
An immersion heater works much like a giant kettle. It heats water inside a hot water cylinder by passing an electrical current through a submerged heating element.
Connected to your electricity supply through a dedicated switch, it can be switched on and off as needed. A thermostat controls the water temperature, while a timer can help schedule heating.
What Is the Difference Between an Immersion Heater and a Gas Boiler?
The key differences are how they heat water and the energy source they use.
An immersion heater is an electric component that heats water directly inside a hot water storage cylinder. It is not a complete heating unit like a traditional boiler.
A gas boiler burns gas to heat water. Depending on the system, it supplies hot water on demand or heats water stored in a cylinder, as well as supplying central heating.
Which Homes Use Immersion Heaters?
Immersion heaters can provide hot water for small and large households. However, installation requires a suitable hot water storage cylinder.
Homes with limited space, such as small apartments without room for a cylinder, may find this arrangement impractical. Properties using a tankless combi boiler would need additional equipment and space to accommodate one.
What Are the Pros and Cons of Immersion Heaters?
Pros of Having an Immersion Heater
Independent Hot Water Heating
An immersion heater can operate independently of the boiler. If the boiler breaks down, a working immersion heater in the cylinder can still provide hot water.
Insulation Helps Save Energy
A well-insulated cylinder retains heat after the immersion heater switches off. This reduces heat loss and the electricity needed to reheat the water.
Timers Can Reduce Running Costs
On an Economy 7 or another suitable time-of-use tariff, a timer can schedule water heating during cheaper electricity periods.
The savings depend on your tariff, hot water demand and how effectively the cylinder retains heat.
Compatible with Renewable Energy Sources
Because they use electricity, immersion heaters can be powered by renewable energy sources, such as solar panels. Using surplus solar electricity to heat water can reduce reliance on grid electricity.
PAD Magazine’s guide to what size solar panel system your home really needs explains how to choose a setup suited to your household.
Easy to Use
Most immersion heaters have straightforward controls. A dedicated switch, thermostat and optional timer make it easy to manage daily hot water heating.
Cons of Having an Immersion Heater
Running Costs Can Be High
Running costs depend on your electricity tariff and usage. Heating a large cylinder with standard-rate electricity can be costly, particularly if the heater runs unnecessarily or the cylinder is poorly insulated.
Safe Storage Temperatures Must Be Maintained
Where temperature is used to control Legionella risk, HSE guidance recommends storing hot water at 60°C or higher. Appropriate controls are also needed to manage scalding risk at outlets.
A qualified professional should advise on the correct settings for your system.
It Does Not Normally Heat Radiators
A standard domestic immersion heater heats the water in a hot water cylinder. It does not replace the boiler’s central heating function, so it will not normally keep radiators working if the boiler fails.
Heating Water Takes Time
Heating a cylinder from cold can take several hours, depending on its capacity, the element’s power and the starting water temperature.
Some cylinders have separate elements or a boost function for heating a smaller upper section. However, a basic setup may heat more water than you need for a small task.
Installing an Immersion Heater
If you think an immersion heater is the right choice for your home, hire a qualified professional to assess the system and install it properly.
Find a local expert by searching for plumbing and heating near me and arrange an assessment.
Although an immersion heater is a standalone component, installation involves plumbing and electrical work. The installer should ensure the element, thermostat, safety controls and electrical connection are suitable for your cylinder.
Final Thoughts
Immersion heaters have advantages and disadvantages. Whether one is right for you depends on your hot water needs, available space, electricity tariff and existing heating system.
They can be useful as backup water heaters or for using surplus solar electricity, but running costs and heating times should be considered.
If you need help deciding or arranging installation, contact a qualified plumber, heating engineer or electrician for advice tailored to your home.
