When it comes to heating water in your home, there are two main options – immersion heaters and boilers. Both serve the same purpose, but they work differently and have different advantages. Choosing the right system can help you save money on energy bills and ensure a constant supply of hot water.
An immersion heater is an electric water heater that sits inside a hot water tank. It works like a giant kettle, using an electric element to heat the water. Many homes use immersion heaters as a backup system, especially in case the boiler breaks down. They are easy to install and work independently of the gas or oil supply. However, they can be expensive to run as electricity costs more than gas.
A boiler, on the other hand, heats water using gas, oil or electricity and delivers it through pipes to taps, showers and radiators. Boilers are also commonly used for central heating. They are more energy-efficient than immersion heaters for larger homes as they heat water faster and cost less to run. However, they do require regular maintenance to keep working efficiently.
At Stillorgan Gas, we specialise in installing and maintaining boilers and heating systems in Dublin. If you're unsure whether a boiler or immersion heater is the right choice for your home, our experts can guide you.
Choosing between an immersion heater and a boiler depends on your home setup, budget and energy source. In this guide, we'll compare both options in detail so you can make the best decision for your home.
For more energy-saving tips, see this SEAI guide on home heating.
What Is a Boiler?
A boiler is a heating system that heats water and sends it to taps, showers and radiators. It works by burning fuel (gas, oil or electricity) to heat the water, which is then distributed through pipes. Boilers are used for both hot water and central heating in homes and businesses.
How Does a Boiler Work?
The boiler heats water inside a tank or through a heat exchanger. The hot water is then sent to taps for use in kitchens and bathrooms. If the boiler is connected to a central heating system, it also sends hot water to radiators to heat the home.
Types of Boilers
Combi Boiler (combination boiler)
Provides both hot water and heating from one unit.
Heats water on demand, so there's no need for a storage tank.
Ideal for smaller homes with limited space.
System Boiler
Stores hot water in a separate tank, making it better for homes with multiple bathrooms.
This works well for larger homes that need a lot of hot water at once.
Conventional Boiler (Regular Boiler)
This requires both a hot water tank and a cold water storage tank.
Suitable for older heating systems or larger homes with large water needs.
Where are Boilers Used?
Homes - Boilers provide heating and hot water for everyday use.
Business - Offices, hotels and restaurants use boilers for heating and laundry.
Industrial - Factories and warehouses need large boilers to heat large spaces.
Key Differences Between an Immersion Heater and a Boiler
Feature | Immersion Heater | Boiler |
Energy Source | Electricity | Gas, oil, electricity |
Efficiency | Less efficient for regular use | More efficient for central heating |
Cost of Installation | Lower | Higher |
Running Costs | Higher due to electricity rates | Lower with gas/oil |
Heat Output | Limited to water heating | Heats water and radiators |
Usage | Backup or supplementary | Primary heating system |
Pros and Cons of an Immersion Heater
An immersion heater is an electric water heater that sits inside a hot water tank. It heats water using an electric element, similar to how a kettle works. Many homes use immersion heaters as a backup or when a gas supply is not available. Below are the advantages and disadvantages of using an immersion heater.
Advantages of Immersion Heaters
✅ Simple installation
Immersion heaters are easy to install and do not require complicated plumbing work. They only need an electrical connection and a water tank.
✅ Works as a backup
If your boiler stops working, an immersion heater can provide hot water until the boiler is fixed. This makes it a useful backup system.
✅ Independent of gas supply
Since it runs on electricity, an immersion heater is ideal for homes without a gas connection. This is useful in remote areas or homes that rely on renewable energy sources such as solar panels.
Disadvantages of Immersion Heaters
❌ Higher electricity costs
Electricity is usually more expensive than gas or oil. Running an immersion heater regularly can lead to higher energy bills.
❌ Slower heating time
Immersion heaters take longer to heat water than gas boilers. If you need a lot of hot water, this may not be the best choice.
❌ Not suitable for whole home heating
Unlike boilers, immersion heaters only heat water and do not provide central heating. You will still need a separate heating system for your home.
At Stillorgan Gas, we help homeowners choose the best heating system for their needs. If you are not sure whether an immersion heater is right for you, contact us for expert advice.
Advantages and Disadvantages of Boilers
A boiler is a heating system that provides hot water and central heating. It heats water using gas, oil or electricity and distributes it through pipes to taps, showers and radiators. Boilers are commonly used in homes and businesses because they are efficient and reliable. However, like any heating system, they have both advantages and disadvantages.
Advantages of Boilers
✅ More energy-efficient for whole-home heating
Boilers are designed to heat water quickly and distribute it throughout the home. They use less energy than electric water heaters, especially if they run on gas. This makes them a cost-effective option for long-term use.
✅ Works with radiators and underfloor heating
Unlike immersion heaters, boilers can provide both hot water and heating. They work with radiators, underfloor heating and even towel warmers, making them ideal for homes in colder climates.
✅ Lower running costs (if gas-fired) Gas is usually cheaper than electricity, so a gas-fired boiler can help reduce energy bills. Although the initial cost of installing a boiler is higher, the savings over time make it a good investment. Disadvantages of boilers
❌ High initial cost and installation Boiler systems require professional installation, which can be expensive. You may also need additional components such as radiators, pipes and a thermostat, which increases the overall cost.
❌ Requires regular maintenance To keep the boiler running efficiently and safely, it needs servicing annually. Neglecting maintenance can lead to breakdowns or reduced performance. Dependent on gas or oil supply If your home relies on a gas or oil boiler, you need a constant supply of fuel. If there is a gas shortage or the price rises, your heating costs can rise.
At Stillorgan Gas, we install, repair and maintain boilers in Dublin. If you’re considering buying a new boiler, contact us for expert advice.
How to Decide Which is Right For You?
Choosing between an immersion heater and a boiler depends on your home setup, energy source and budget. Both systems provide hot water, but they work in different ways and cost differently. Here's how to find out which one is best for your needs.
Best for Homeowners With a Gas Supply
Boiler If your home is connected to gas, a gas boiler is the best option. It provides hot water and central heating efficiently. Gas is cheaper than electricity, so running a boiler costs less in the long run. Boilers also heat water quickly, making them ideal for households that use a lot of hot water.
Best For Homes Without a Gas Supply
Electric boiler or immersion heater If your home doesn't have a gas connection, you have two options: Electric boiler - works like a gas boiler but runs on electricity. It provides heating and hot water but costs more to run. Immersion heater – heats water using an electric element. It's cheaper to install than a boiler but costs more to run.
Best as a Backup Heating Option
Immersion heater : If your main boiler fails, an immersion heater is useful as a backup. It can still provide hot water if your boiler is broken or undergoing maintenance. Many homes with a gas boiler have an immersion heater as a secondary option.
Best for Energy Efficiency and Whole House Heating
Boiler : A boiler is the best choice for heating a whole house, as it works with radiators and underfloor heating. It's more energy efficient than an immersion heater and costs less to run over time, especially if it's gas-powered.
Cost Comparison and Energy Efficiency Considerations
When choosing between an immersion heater and a boiler, it's important to compare cost and energy efficiency. The right choice will depend on your budget, energy source and long-term savings.
Initial Installation Costs
Immersion heater - cheaper to install as it only requires a hot water tank and electricity connection. A simple installation can cost a few hundred euros.
Boiler - more expensive to install, especially if you need new pipes, radiators or a thermostat. Gas or electric boilers can cost between €2,000 and €4,000 or more, depending on the type and size.
Long-term Running Costs
Immersion heater - uses electricity, which is usually more expensive than gas. Running an immersion heater regularly can increase your electricity bill.
Boiler - if powered by gas, it's cheaper to run than an immersion heater. However, oil or electric boilers can be more expensive.
Energy Efficiency Ratings and Sustainability
Boilers have an energy efficiency rating from A to G (A being the most efficient). Modern condensing boilers use less fuel and waste less heat.
Immersion heaters are 100% efficient (all the electricity is used to heat the water), but because electricity is expensive, they are less economical for everyday use.
If powered by renewable energy (solar panels), an immersion heater can be a greener option.
The Impact of Rising Energy Prices
Electricity prices are rising, making immersion heaters more expensive to run over time.
Gas prices also fluctuate, but a gas boiler still remains the cheaper option for most homes.
Frequently Asked Questions About Immersion Heaters and Boilers
When choosing between an immersion heater and a boiler, many homeowners have common questions. Below are answers that will help you decide which system is right for your needs.
1. Can I Use Both an Immersion Heater and a Boiler?
Yes, many homes have both systems. The boiler is used as the main source of hot water and heating, while the immersion heater serves as a backup. If the boiler breaks down, the immersion heater ensures you still have hot water.
2. How Long Does it Take for an Immersion Heater to Heat Water?
Heating time depends on the size of the water tank and the power of the heater. On average, an immersion heater takes 1 to 2 hours to fully heat a large water tank. Some newer models heat water faster, but they still take longer than a boiler.
3. Which Option is Better For a Small Apartment?
For small apartments, a combi boiler or electric boiler is usually the best choice as it heats water on demand and doesn't require a large water tank. An immersion heater can come in handy if space is very limited, but it may not be economical for daily use.
4. Do immersion Heaters Need Servicing Like Boilers?
Unlike boilers, immersion heaters don't need regular servicing. However, over time, limescale can build up on the heating element, especially in areas with hard water. Cleaning or replacing the element every few years can help maintain efficiency.
At Stillorgan Gas, we install and service boilers and heating systems in Dublin. If you need advice on heating solutions, contact us today!
Conclusion
Choosing between an immersion heater and a boiler depends on your home’s heating needs, energy source, and budget. Both systems provide hot water, but they work differently and have different costs.
Key Differences Recap
Boilers are the best choice for whole-home heating and hot water. They are more efficient and cheaper to run if powered by gas.
Immersion heaters are simple, independent from gas, and good as a backup option. However, they have higher running costs due to electricity usage.
Final Recommendations
Choose a boiler if you need central heating and regular hot water. A gas boiler is the most cost-effective for most homes.
Choose an immersion heater if you need a backup system or live in a home without a gas connection.
If you have a small apartment, an electric boiler or immersion heater might be a better space-saving option.
If you’re concerned about energy costs, a modern A-rated boiler will save money in the long run.
Consult a Heating Expert
Every home is different, and the best choice depends on your energy source, water usage, and budget. At Stillorgan Gas, we specialize in boiler installation, servicing, and heating solutions in Dublin.
If you’re unsure about the best system for your home, contact us today for expert advice!
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