Are you considering changing from a conventional boiler to a combi and wondering whether it’s worth it? Read on to discover how a conversion can benefit your household.

Condensing combi boilers have become increasingly popular. Statistics show that over 54% of households in England use combi boilers to heat their homes and hot water.

Conventional boilers are traditional types of boilers usually found in many older-built homes.

Greater energy efficiency is one of the main advantages of changing from conventional boilers to combi.

If you’re struggling with an old, broken, or inefficient boiler, replacing it with a modern combi boiler can save you money on fuel costs and help reduce your carbon footprint.

This guide explores everything you need to know about changing from a conventional boiler to a combi, including costs, common scenarios you can expect, and whether it’s worth it.

Quick Takeaways:

• Combi boilers can provide hot water and central heating from a single, compact unit and are suitable for the average UK home.
• Unlike conventional boilers, they don’t require a separate water tank or cylinder.
• Changing from a conventional boiler to a combi can improve efficiency, save space, provide instant hot water on demand and high water pressure, and reduce the risk of breakdowns and repairs.
• Changing from a conventional to a combi boiler requires more time, materials, and labour than a like-for-like swap.
• You can expect to pay anywhere from £2,000 to £3,000.

What Is A Combi Boiler?

A combi (short for combination) boiler is designed to provide hot water and central heating from a single, compact unit.

It can provide hot water on demand, meaning you can get it almost instantly if you turn on your tap.

This is a unique feature not found in boilers that utilise a hot water tank, in which case you would have to wait for the water to heat up before using it.

A combi boiler doesn’t have a tank. Instead, it takes cold water directly from the mains and heats it as and when needed.

Cold water is drawn into the boiler as you turn your tap on. It’s then heated up via the heat exchanger, which transfers the heat from the burning gas to the cold water.

Combi boilers’ installation options are more flexible than conventional boilers, as they do not have to be installed close to a larger storage tank.

They’re ideal if you live in a smaller home with limited living space for a water cylinder. The cold water storage

What Is A Conventional Boiler?

Conventional boilers, called regular or heat-only boilers, have separate cold water storage tanks and hot water cylinders.

The cold water storage tank is placed as high as possible, usually in the attic or loft, to help increase water pressure. The hot water storage cylinder can be stored in an airing cupboard.

Conventional boilers are suitable for larger homes with high hot water demands. However, you must wait for the cylinder to fill up and heat water whenever you run out.

Wondering how much a new boiler costs? Check out our guide on options available if you need a new boiler but can’t afford it, as well as boilers on finance and government boiler grants here.

Why Change From Conventional Boiler To Combi?

A combi boiler is suitable for most household properties in the UK, making it the most popular type of domestic boiler.

Some of the most important reasons for changing from a conventional boiler to a combi include:

Boiler Efficiency

Modern combi boilers are extremely energy efficient, as our boiler ERP efficiency guide explains.

They’ll have higher efficiency than older, conventional boilers mainly because they’re condensing.

Condensing boilers recover more heat from the exhaust flue gas and use it to heat the central heating water, making them more efficient than older boilers. In fact, modern combi boilers are A-rated, which means they’re over 90% efficient.

In financial terms, for every £1 you spend, only 10 pence is lost, which is extremely good compared to boilers that were only 70% efficient 10 years ago.

This efficiency difference means combi boilers are better for the environment as they release less carbon dioxide.

This also means they use and waste less fuel, which means you will save money on your energy bills.

Are you wondering which boiler manufacturers performed best? Check out our guide to the best boiler brands for the full rundown. If you’re trying to determine the best boiler installation company, check out our Warmzilla and Boxt reviews.

Check out our video on how to vet boiler brands/models in the UK:

Saving Space 

If you have a property with limited space, a combi boiler is one of the most compact types of boilers, so it’s ideal for you.

In fact, some newer combi boilers are marketed as being “cupboard size.”

Conventional boilers are, on average, much larger and don’t provide hot water on demand. They require a hot water storage tank, which takes up considerable space.

Additionally, combination boilers require less pipework than conventional boilers and are ideal for smaller and medium-sized properties.

What size boiler is right for your home? If you are considering a combi boiler, it is largely determined by the number of radiators in your home.

Check out our complete guide to new boiler installation here if you are wondering about the best type of boiler for your home. 

How much may a new boiler cost? Are you considering converting from a conventional to a combi boiler? Use our boiler installation cost calculator to get an estimation.

Less Risks of Repairs & Breakdowns

Older boilers are prone to regular breakdowns and repairs. Boilers have many moving parts that are regularly exposed to heat.

Over time, the parts deteriorate due to normal aging and eventually fail, making replacing or repairing them necessary.

The warranty for an old boiler will likely be voided, so you’ll have to pay for any major repairs and emergency call-outs. Repair or part replacement costs can quickly add up and reach or exceed the costs of a new boiler.

Therefore, replacing your old conventional boiler with a new combi model can make more financial sense to avoid constant repairs and the inconvenience of an unreliable boiler.

Instant Hot Water On Demand

Running out of hot water can be a nightmare, especially during winter.

Conventional boilers don’t provide hot water on demand, and you may experience sporadic shortages when the tank empties and have to wait for the large volume of water stored in a tank to heat up.

However, a combi boiler never runs into this issue. It does not have a hot water tank that can empty and needs to be refilled.

Instead, a combination boiler can provide instant hot water by heating the water as soon as you turn on the hot water tap.

Easy to Service

Combi boilers are more accessible to service and repair since everything is housed in one unit.

No complicated external parts could malfunction or break, and thanks to their popularity, replacement parts are easier to source and cheaper than hard-to-find parts.

Most heating engineers are also trained to work with combi boilers, so you can easily find a qualified one in your area.

High Water Pressure

Combi boilers take their water supply directly from the mains, meaning they retain much of the mains pressure for normal water pressure in your taps and showers.

A traditional heating system often relies on gravity to collect water. A combi’s flow is much stronger, and the extra force behind the flow reduces the likelihood of water becoming stuck or ‘pooling’ in curved pipes.

Compatible with Smart Tech

Due to their modern and consumer-convenience-based design, many combi boilers can be synced with and remotely controlled by technology, such as smart thermostats or apps, via a smartphone or tablet.

This allows for wireless temperature regulation and control on the move, and some apps can even detect component faults and automatically notify an engineer. 

What Is Involved In Changing From Conventional Boiler To Combi?

Changing from a conventional boiler to a combi is more complicated than a normal combi boiler swap or replacement. It will require more time, materials, and labour, which can influence the final cost.

Remember, this is not a DIY job. Not only is this job incredibly difficult for the newbie, but it’s also illegal to carry out any type of work with a gas appliance unless you’re qualified and registered to do so.

Therefore, getting your boiler installed by a registered gas-safe engineer is crucial.

Things a Gas-safe engineer does during a swap from a conventional boiler to a combi include:

• Cleaning the current central heating system.
• Removing the current conventional boiler and storage tank.
• Removing associated controls.
• Inspect the existing pipework to determine if any faults can compromise the combi boiler.
• Installation of the new combi boiler and any required pipework.
• Powerflush on the entire boiler system and installation of magnetic or limescale filters for hard-water areas.
• Installing new smart thermostats to help prevent energy waste.
• Testing the new combi boiler system to ensure it’s running correctly. The gas engineer will also provide tips on using and maintaining your combi boiler.

Did you know your boiler’s efficiency can impact the energy it uses and, ultimately, your heating bill costs? Check out our guide to the best condensing boilers to learn more. 

Costs Of Changing From A Conventional Boiler To Combi Boiler

As mentioned earlier, the exact cost of converting from a conventional boiler to a combi boiler can vary.

In general, the costs will be impacted by the following factors:

• If you want to move your boiler to a new location in the house.
• The brand of the combi boiler you opt for, such as a premium model vs. a value model.
• The size of your property and how much pipework is involved.

With that in mind, you can expect to pay anywhere from £2,000 to £3,000 on average.

Remember, you should get various quotes before making a final decision.

Got a common boiler problem? Check out our quick-fix guide on boiler lockout, ignition faults, PCB faults, faulty diverter valves, and boiler timer issues.

Here are some general guidelines for the costs of different types of common boiler installations:

• The cost of replacing a system boiler with a combi boiler can range from £2,000 to £2,500, and the replacement process can take two days.
• Converting a regular boiler to a combi boiler can cost from £2,300 to £2,600. The replacement process takes two days.
• Replacing a back boiler with a combi boiler costs £2,500 to £3,200 and takes 2 to 3 days to complete.
• Converting an old combi boiler to a new one can cost from £2,000 to £2,500, and the replacement process takes around two days.

Additionally, you can expect to pay a little more to have your tank removed from the property, as this involves more time and labour.

On average, removing a storage tank will cost around £150, and £ a header tank (typically located in the loft) will cost around £ 200.

Which is the Best Combi Boiler? 

With so many boilers on offer today, it can be very difficult to know exactly which one to choose. However, these are some things you should pay attention to:

• Warranty period – How long is the warranty offered? Ideally, it should be 10 years, which means repairs and callouts will be covered. You can get cheaper boilers, but they often have a much shorter warranty period.
• Boiler size, e.g., kW output—Is the boiler large enough for your property? Make sure not to undersize or oversize your boiler.
• Physical dimensions – The size, e.g. physical dimensions, is equally important as it will need to fit where you intend it to be installed.

Although you may find cheaper boiler deals on cheaper brands with shorter warranties, it’s important to consider if this is really worth it in the long term.

A shorter warranty often indicates poorer quality, so this is worth remembering.

Got a common boiler problem? Check out our quick fix guide for boiler lockout, ignition faults, PCB faults, faulty diverter valves, and timer issues.

You may also find our review of the best eco-friendly boilers of interest.

Check out our boiler brand price guides and comparisons:

• British Gas new boiler costs.
• How much is it to fit a new boiler?
• How much does a Vaillant boiler cost?
• Baxi boiler costs.

Changing From Conventional Boiler To Combi Conclusion

In many situations, replacing your conventional boiler with a modern combi boiler will be well worth the investment, but you should be prepared to invest a little more than you would if you were getting a typical like-for-like replacement.

The bottom line is that combi boilers are extremely compact, ultra-efficient and easy to service, repair and maintain.

Sources and References

• https://www.statista.com/statistics/292259/boiler-types-in-dwellings-in-england/