Among 95% of UK homes that are centrally heated, the majority use gas or oil-fired boilers. This is the conventional heating system that prevails in most households. Most people won’t think of replacing it unless absolutely necessary.
However, if you want to shift to a more efficient and eco-friendly option than the gas-guzzling machine, you need to assess the feasibility. A combination boiler (combi boiler) provides hot water and centralised heating from a single unit. You might also look for a shift because your existing one is too old to meet your heating requirements.
Since the boiler is one of the most critical appliances in your home, you would want something efficient yet energy-saving. Though installing a combi system requires an initial hefty cost, the long-term benefits are far-reaching and appreciable.
We will discuss in detail the feasibility of replacing your conventional boiler with a combi system so that you can make a well-informed decision.
What Are The Differences Between A Conventional And A Combi Heating System?
Conventional or Regular Boilers
Around 90% of UK homes have gas boilers with radiators. This conventional system has centralised heating, where water is stored in a cylindrical tank. They are often known as ‘heat only’ boilers because they only produce hot water for central heating, but not for domestic use like taps, baths, or showers.
Here, cold water is stored in a water storage cistern that is usually placed above the boiler, like in the attic. When the boiler is fired up, that cold water is then warmed up by a heat exchanger.
The heated water gets pumped to a hot water storage cylinder, where it is stored and circulated until you need it. The valves carry the hot water to your taps and other outlets.
Combi Boilers
A combi is a single-unit boiler that heats the space and produces hot water. Nowadays, many UK homes are upgrading to this efficient system.
Here the water heats up directly when you connect it to the primary water source. So, when you turn on the connected outlet valves, you will have hot water available on demand without waiting for any storage tank to fill.
Why Are Combi Boilers Becoming A Popular Choice?
1) Energy efficiency: One of the most important reasons for opting for a combi boiler is energy efficiency. According to the Energy Saving Trust, replacing a 12-15-year-old boiler with a new A-rated condensing combi boiler can help you save up to 40% on energy bills.
2) Compact Size: Conventional boilers need a much bigger space for the tank and cylinder. The storage is usually above the boiler, placed in an attic, and you also need space for the storage units.
On the contrary, the compact size of combi boilers is ideal for even the smallest of properties. Since they use the mains as the water source, you do not need a dedicated space for a water tank or cylinder. The smallest ones are often marketed as “cupboard-fit” combi boilers.
3) On-demand supply: Combi systems provide on-demand hot water as they instantly heat the water. You do not have to worry about having enough water in the hot water storage tank or it running out. Hence, you do not have to wait for a long time like with a conventional boiler.
4) Flexibility of location: Since a combi system is a relatively smaller single unit, they have the flexibility to be installed anywhere in the house. Systems and regular boilers require a storage tank or overhead tank, which omits many options.
Conventional boilers are usually noisier and can leak carbon monoxide; for older models, it is difficult to find replacement parts. These are other reasons people would look for an alternative to regular boilers.
Internal components of a boiler corrode due to regular wear and tear. This brings down the efficiency of a non-condensing boiler to 70% to 50% over the years. In financial terms, it means losing £30 to £50 of every £100 expense on your energy bills.
Shifting to a combi boiler, especially the A-rated condensing combi boiler can save that money as they are over 90% efficient. Some premium combi boilers like the Viessmann Vitodens 200-W are even 98% efficient or more.
The best way to determine if your conventional boiler needs replacement is to get a thorough checkup done by a professional engineer. They will be able to assess the efficiency and your requirements to suggest a better fit for your home.
But how much does a combi boiler cost and what is the overall cost of replacing a conventional one? Let’s find out more.
How Much Does It Cost To Replace A Conventional Boiler With A Combi Boiler?
A new combi boiler may cost between £500 and £2,000 depending on the brand, type of model, size (output rating), efficiency, warranty length, special features, etc. This excludes the installation cost.
The below table will give you a fair idea of the price range of different models:
| Type of Combi Model | Price Range |
| Budget models | £500 – £900 |
| Mid-range models | £900 – £1,200 |
| Premium models | £1,000 – £2,000 |
Source: boilerguide.co.uk
You can use the below criteria to narrow down the options:
- kW output – It determines if the boiler is powerful enough for your property.
- Physical dimensions – It will help you check the feasibility of installing it in a cupboard-size space.
- Warranty – It allows you to see the value for money and the longevity of the product.
The installation cost depends mainly on the engineer’s rates, the location, and the complexity of the installation. (Note: The installation cost of a gas combi boiler for a small-medium property can range between £1,800-2,200. It includes a complete replacement, where you get a new boiler to replace an old one of the same type.)
In other cases, you can expect to spend approximately £3,500 to replace a conventional boiler with a combi, including the pipework setup, reconfiguration, and removal of the hot water storage cylinder and the feed water tank.
| Boiler Replacement Situation | Estimated Cost |
| Replace an old combi boiler with a new one, in the same location | £1,700 |
| Replace a system boiler with a new combi boiler, including the removal of the hot water cylinder | £2,500 |
| Replace a regular boiler with a new combi boiler, including the removal of the hot water storage and cold water tank | £3,500 |
Source: boilerguide.co.uk
The best way to compare and contrast to decide is to get a quote from at least three or more local vendors.
Requesting quotes online is a good idea because:
- It saves both time and effort.
- It eases getting a quote by simply filling out a form anytime.
- It makes the comparison process easy for better decision-making.
What are the other overhead costs required for the installation?
The replacement cost of a combi boiler increases when the workload increases for an appliance installation or replacement project.
These are a few necessary checks that an engineer needs to do before you get a final estimate for replacing a conventional boiler with a combi boiler:
- A shift in boiler location
- Adhering to new norms of gas fuel standardisation
- Drilling of holes for the new system
- Installation of a magnetic system or limescale filter, depending on water quality
- Upgradation of heating controls
- Removal of the storage tanks of the conventional boiler (the cost can range between £100 to £300)
How Long Does It Take To Change To A Combi Boiler?
A boiler conversion takes a longer time than a straightforward combi swap. On average, it might take two days to complete, but this can vary depending on the complexity of the job. For a like-for-like replacement, it might just take a day.
If you have recently purchased a new house, your current conventional boiler is beyond repair, or it is more than 12 years old and not as efficient, you can consider replacing it with a combi boiler. Combi boilers are effective because they give both space heating and water on demand, without storage. Besides being more efficient in energy and storage, they are also a greener choice.
