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What is a Combi Boiler? A Full Explanation and Details for 2024
- From: Kevin Smith
- Published 1 November 2024
Key Takeaway
- The Combi boiler, short for combination boiler, provides both heating and hot water within a single, compact system.
- They are most in demand due to their compactness, efficiency in performance, and capability of providing a constant supply of hot water.
- Depending on the brand and model, new combi boilers cost anywhere between £500 to £3,000.
- With regular maintenance, they could last upwards of 10-15 years.
The combination boiler, or combi boiler, is one of the most popular – or we must say one of the top choices – for home heating in the UK. These provide heating and hot water from one same compact unit. This feature has made it a popular choice for modern homes, especially because it doesn’t require bulky tanks or cylinders. Most combi boilers are small enough to fit into one of those kitchen cupboards, which is a bonus when space is tight.
And if you want to upgrade, the ECO4 Scheme is your chance to do so. This government scheme may well cover the full cost of a brand-new, energy-efficient boiler, allowing such eligible homeowners and tenants to enjoy an even more comfortable, affordable heating system with no upfront cost.
In this guide, we will explain combi boilers in detail.
What is a Combination Boiler?
A combination or combi boiler is a small-sized heating unit; it does two jobs simultaneously: heats the water of your home and powers the radiators for central heating. Because it performs all the operations within one unit, it is easier to install and operate than traditional systems, which require supplementary components in the form of hot water cylinders.
Because the combi boiler connects directly to the mains, it will only heat water when it’s needed-whether you’re running a bath or turning on the heating. However, this very feature of on-demand use saves both space and energy, which is just why it is one of the most popular choices in the UK.
How Does a Combi Boiler Work?
It may sound complex, but the job the combi boiler does can be quite straightforward. When a tap or the heating is turned on, the boiler fires up. Inside, here’s basically what happens:
1. Ignition and Heating
It ignites a burner inside the boiler and heats up the primary heat exchanger. It transfers some of the warmth through to the water passing by using one of the heat exchangers.
2. . Heating and Hot Water
A diverter valve is responsible for directing heated water to your radiator (for central heating) or to your taps (for hot water).
3. Continuous Supply
This system allows a continuous flow of hot water directly from the mains. You’ll have instant hot water at all times, though possibly with a slight fall in pressure if there are various taps or showers on at the same time.
New combi boilers use condensing technology, wherein heat from the exhaust gases is inherently recovered to boost efficiency even more. Some include a feature called “pre-heat,” where a small amount of water is always hot in the boiler so that when you need it, it will be there without delays.
What Type of Heating is a Combi Boiler?
A combi boiler is short for “combination boiler.” It means that your central heating and the hot water come from one unit. Just think about having both the heating system and the hot water coming from the same unit – think neat, right?
This compact setup does not require any bulky tanks or cylinders; hence, it is ideal for people with limited space. Most combi boilers are wall-mounted and can easily be tucked away into a kitchen cabinet.
Moreover, combi boilers are very efficient. With the help of condensing technology, as many combi boilers do these days, they recover heat that would otherwise have escaped through the flue. Consequently, this means less energy is used, which is good for the environment and thus will keep your bills in check. If you look after it well with regular servicing, a combi boiler can last you a good 10 to 15 years.
Is a Combi Boiler Right for Your Home?
Combi boilers work exceptionally well in small to medium-sized properties with one or two bathrooms. They won’t quite fit homes needing lots of hot water at the same time, which means none of these units are suitable for extensive households with several bathrooms. Still, there are high-capacity models available on the market for bigger homes.
Combi boilers are just a natural choice if you are staying in a flat or a smaller house. They are compact and convenient without the clutter of tanks or cylinders. With schemes like ECO4, eligible homeowners can benefit from a free boiler upgrade that could make switching to a combi boiler even easier.
Upgrade Your Boiler For Free
If you or any of your household is on benefits, you may be eligible for boiler upgrade grant.
Combi Boiler Types Based on Fuel Used
In basic design, all Combi boilers are essentially the same. Bith respect to the type of fuel used, they differ. Currently, four main types of Combi boilers exist for different needs and household settings: gas, oil, LPG, and electric.
1. Gas Combi Boilers
Gas Combi Boilers are the most common type used in the UK, operating off natural gas supplied by the national grid. Households and businesses alike utilise this type, as it is reasonably priced and reliable. The raw material required for it – natural gas – is easily available at a cheap rate.
While natural gas is a fossil fuel, it is cleaner than oil or coal. In fact, the condensing technology utilised in the gas combi boiler directs and reutilises the lost heat energy for even greater efficiency and a reduction in CO2 emissions. It keeps energy usage at a minimum, which would certainly let you save on energy bills and decrease your environmental impact.
2. Oil Combi Boilers
Oil combi boilers are practical if one lives in a house that has not been connected to the gas grid. While cost-effective, they need an external oil tank for fuel storage. This constitutes the fact that this type may occupy more of the garden space or even underground, depending on the type.
Unlike gas, oil needs to be stored and refilled from time to time. That means you will need to plan ahead and make sure that you do not run out of fuel. They also have condensing technology to make them efficient. Still, oil combi boilers are more intensive in emissions compared to gas boilers, and this is reflected in their impact on the environment.
3. LPG Combi Boilers
LPG combi boilers represent a a cleaner option than oil, thus being ideal for those properties that have no main involving gas. This is derived from the extraction process of both natural gas and oil, which makes it cheap and widely available.
Most of the major boiler manufacturers now make models compatible with LPG, so you do have quite a few options with this fuel type. Although LPG is seemingly cleaner than oil in its emissions rate, it’s not as clean as natural gas. However it is still reliable to provide heat and hot water without the high-emission intensity of oil.
4. Electric Combi Boilers
Of all types, electric combination boilers are the most efficient; one can achieve 99-100% efficiency from them because every bit of electricity gets converted into heat with absolutely no wastage. They do not require a flue and so are ideal to fit in areas where access to ventilation is not possible.
While efficient, electric combi boilers are usually more expensive to run because of the high cost of electricity. Again, they will only achieve a zero-emission status when combined with renewable energy sources such as solar panels or electricity from a green energy source.
Environmental Impact of Combi Boilers in the UK
The overall environmental impact a combi boiler has greatly depends on the type of fuel it uses. Since we want you to make an eco-conscious choice, here’s a quick look at how their measurement in terms of emission goes for gas, oil, LPG, and electric combi boilers:
Upgrade To Combi Boilers For Free
If you or any of your household is on benefits, you may be eligible for boiler upgrade grant.
Emissions by Fuel Type
The statistics from the Energy Saving Trust for its emission intensity vary according to which fuel is used by type of boiler-per unit of energy used:
- Gas: 0.213 kg CO₂ per kWh
- Oil: 0.298 kg CO₂ per kWh
- LPG: 0.240 kg CO₂ per kWh
- Electricity: 0.225 kg CO₂ per kWh
Worth noting, though, is the fact that such emissions from electricity assume the current national mix of the grid stays on, which has a fair amount of fossil fuels. If you power your electric combi boiler with renewable energy – say, solar – then its carbon footprint becomes radically reduced.
How Does a Combi Boiler Fit in Your Central Heating System?
One of the major advantages of a combi boiler is its simplicity. Whereas system boilers, for example, need a different hot water cylinder and a regular boiler needs a cold-water storage tank, combis do not. Besides saving space, this design makes for minimum heat loss, for one does not have to maintain a cylinder full of hot water at the ready. You get hot water on demand, hence reducing energy wastage.
Cost of a Combi Boiler in the UK
In the UK, the cost of a new combi boiler swings greatly and usually falls in the bracket of £500 to £3,000. If you cannot afford a new combi boiler and receive specific government benefits, you may be qualified to get a free boiler grant under the ECO4 Scheme.
The following are the main factors influencing the cost of combi boilers:
1. Brand and Model
A reputed brand will cost more but usually offers reliability and customer service benefits. The models vary from budget, mid-range, and premium category with flexibility depending on preferences and needs.
2. Fuel Type
Combi boiler can be operated on gas, oil, LPG, and electricity. Generally speaking, the gas and electric models have low purchase prices. However, the fuel costs and their availability are some considerations among related things.
3. Installation Costs
Combi boiler installations can range from £1,600 and £3,500, depending on the location and complexity.
4. Warranty
Larger and high-quality models can offer longer periods, thus raising the initial price, but will provide more confidence in the lifetime of the boiler.
5. Other Accessories
While the unit cost of the boiler is the most important, there is the installation of accessories like smart thermostats and other parts, such as magnetic filters that may also add to the overall cost. Still, you should include them in your budget because these peripherals do improve the operation and efficiency of your boiler.
Advantages of a Combi Boiler
Combi boilers are among the most preferred types of boilers, and there are many reasons for choosing such:
1. Compact in Size
Combi boilers are very space-efficient, as they have no requirement for an external tank or cylinder. They can fit in small areas such as kitchen cupboards or airing cupboards. This seems to make installation easier, too, as they integrate right into your space upon installation.
2. High Efficiency
Combi boilers are now, arguably, among the most efficient heating systems. Many of its various models reach an efficiency of 92%, which means that from every £1 you spend on energy, only 8p is being wasted. Comparatively speaking, a much older model may be only 60-70% efficient. Upgrading to a combi boiler could save you quite some amount of money over time in energy costs.
3. Lower Energy Bills
The savings on energy bills are because of the efficiency of a combi boiler. If you have an old, inefficient boiler, this can be replaced by a new, highly efficient combi in a detached home to save about £630 every year. Savings will depend upon the size of the property, insulation, and many other factors, including the efficiency level of the boiler.
4. Hot Water on Demand
Another unbeatable thing that can be said about a combi boiler is the way it can provide you with hot water any moment you need it. Apart from combi boilers, most of the other types of boilers store a fixed amount of hot water; but combis heat water instantly, so there is no waiting around or running out during a shower.
5. Longevity
With proper maintenance, a combi boiler may last anywhere from 10-15 years. Many manufacturers offer a 10-year warranty for peace of mind that your boiler will reliably become part of your home heating system.
Disadvantages of a Combi Boiler
While there are a variety of advantages associated with combi boilers. But they may still not be suitable for every UK household. Here are several possible drawbacks:
1. Not Suited for Large Houses
Combination boilers are not that efficient when there is a need for large volumes of hot water, say, in large homes with many bathrooms. In such scenarios, pressing showers or opening several taps then results in reduced water pressure and lower temperature. This could easily be resolved in larger households by fitting a system boiler with an independent hot-water tank.
2. Dependence on Mains Water Pressure
Combi boilers are dependent on mains water pressure. As such, if the water pressure of your home is low, it automatically impacts negatively on the boiler performance, especially if outlets are to be used at once.
3. Incompatibility with Old Pipework
If you’re upgrading an older heating system, you’ll need to ensure that the pipework can bear up to a combi boiler mains water pressure. It is also absolutely essential that updates of the older pipes be done to avoid problems.
Key Considerations When Choosing a Combi Boiler
It is not just a question of the cost of a combi boiler, as there are several other things to consider, including:
1. Brand
Besides all that, picking a reputable brand can provide some security. Reputable brands usually produce really good products. And when something goes wrong, their customer support is quite responsive and ready to help in urgent situations.
2. Output Rating
Combi boilers are rated by the kilowatt output, which directly influences both price and performance. Higher-rated boilers (28-34 kW) tend to be best suited to larger homes and, thus, will cost more.
Home Size | No. of Radiators | Central Heating Output |
Up to 4 Bedrooms | 10 Radiators | 24-27 kW |
4-5 Bedrooms | 10-15 Radiators | 28-34 kW |
5+ Bedrooms | 15-20 Radiators | 35-42 kW |
3. Type of Fuel
The combi boiler can be either gas, oil, LPG, or electricity-fueled. Each has its own advantageous and not-so-desirable side. Hence, you need to choose the right one for yourself according to your needs.
4. Efficiency
Most modern gas combi boilers achieve A ratings, with efficiency percentages standing at around 92-94%. Electric combi boilers can reach as high as 99-100% efficiency. However, they may have a lower ErP rating due to the carbon-intensive nature of electricity generation.
5. Warranty
The duration of the warranty is dependent on several factors, including the manufacturer and model. If you choose the boiler with a long warranty, then this may well carry over into the far future for possible repairs. Therefore, it will be valuable in long-term peace of mind.
The Bottom Line
A combi boiler is ideal for space-saving, efficiency, and ease of operation within your home. It gives you instant hot water. So, you never have to be concerned with cold showers or heat up a tank of water.
Plus, with an ECO 4 boiler grant, you can upgrade to a modern, energy-efficient model free of charge. It’s the easy way to keep your home warm, cut your energy bills, and do your bit for the environment all at once.
Frequently Asked Questions
Most combi boilers will last around 10-15 years if properly maintained. So, having one annual service helps ensure that it runs safely and effectively. And it catches potential problems before they become expensive repairs.
The Combi boilers are mainly used in homes, where they offer both central heating and hot water. They are ideal for UK households since most of the houses don’t have space to fit in a hot water tank. Hence, they work wonders for small and medium-sized houses.
The main difference is that the combi boiler integrates heating and hot water in one unit. In contrast, the regular boiler has separate parts – a water cylinder and often a storage tank. Combi boilers do not need either of these, which makes them compact and convenient.
“Combi” is short for “combination” since these boilers combine the water heater and central heating in one unit. That means you get hot water and heating from one single piece of equipment.
