Thinking of replacing a heat-only boiler with a combi?
If your existing heat-only or regular boiler is getting old; or is on the blink; you might be considering switching to a combi boiler.
But changing to a combi can be daunting if you’ve never had one before.
It can feel tempting to just replace like-for-like, rather than stepping into the unknown. Particularly if you’ve always had a particular type of boiler.
But there might be a much better suited boiler for your home.
So, when it’s time to replace your boiler; you should ask yourself whether your lifestyle has changed over the last decade. And whether a different sort of boiler might be a better fit for you now.
If you’re wondering whether to change from a heat-only boiler to a combi, this guide will help! We look at the main benefits and drawbacks of making such a switch, to help you with your decision.
For tailored advice, contact one of our friendly team at The Heating People to book your free survey.
Your existing heat-only system
First off, it’s important to establish what your existing heating system is, and what you’re looking for.
This can be a bit confusing, because heat-only boilers are also referred to as ‘regular boilers’ and ‘conventional boilers’. But whichever name is used, we’re talking about the same heating system.
We prefer to call them heat-only boilers. Because they produce hot water for your central heating; but use a separate hot water cylinder to produce hot water for your taps; baths; and showers.
What is a heat-only boiler?
Heat-only boilers are often thought of as the traditional way of heating a home. And out of the three types of boiler available (heat-only, system and combi) they take up the most space.
If you currently have a heat-only boiler; you’ll have noticed the hot water cylinder, which is usually placed in an airing cupboard.
But you might not have seen that there is also a cold water cistern (sometimes called a header tank); and a small feed and expansion tank in your attic or loft space.
These components work together to provide you with heating and hot water.
The cold-water cistern is provided with water from the mains. With the help of gravity, this cold water is fed down to your cylinder.
Your boiler heats this water;, and the cylinder stores it until it’s needed by your radiators, taps or showers.
The feed and expansion tank is used to keep the water in your heating system at the correct level. It allows for the water expansion when the heating is switched on.
What are the main advantages of a heat-only boiler?
Since heat-only boilers store large quantities of hot water in a cylinder; they can meet a high demand for hot water.
This makes them a great choice for larger homes with multiple bathrooms. Or homes where family members all want to use the hot water at the same time.
Heat-only boilers also work well in areas that suffer from low pressure. And they’re compatible with renewable technologies, such as solar – which are vital in our ambition to meet Net Zero.
And if you’re someone who worries about being in the dreaded no-hot-water situation; heat-only boilers can be fitted with an additional immersion heater. This will heat your water in the event of a break-down.
What are the drawbacks to having a heat-only boiler?
If you’re thinking about switching to a combi boiler, you’re probably already aware of the drawbacks of a heat-only boiler.
As we’ve mentioned, heat-only boilers take up a lot of space in your home; because of their additional cold water tanks and cylinders.
And since heat-only boilers store hot water, their ability to supply it is limited by the size of the cylinder.
You might have encountered this problem if you’ve used a lot of hot water in one go. If you completely empty the cylinder, you’ll temporarily run out of hot water until the boiler heats up some more.
The other drawback is that heat-only boilers tend to be the least efficient of all the boiler types. This is because they have the fewest control options, and will experience some heat loss from the hot water cylinder.
To read more about the pros and cons of heat-only boilers, check out our related blog here.
Now let’s take a look at your combi alternative…
How does a combi boiler work?
Combi boilers are currently the most popular type of domestic boiler installed in the UK. We’ve dedicated a whole blog to what they are, which you can read in full here.
But in a nutshell…
A combi boiler provides a ‘combination’ of heating and hot water from one compact appliance; without the need for any external tanks or cylinders.
This differentiates them from system boilers, which require a hot water cylinder; and from heat-only boilers, which require a hot water cylinder and two cold water storage tanks.
Combi boilers don’t need hot water cylinders because they heat water instantly when you turn on a tap; so they don’t need to store it.
They don’t need cold water tanks because (like a system boiler); they take their cold water directly from the mains supply.
What are the benefits of installing a combi boiler?
Combi boilers are very popular in the UK because they offer a lot of benefits:
Combi boilers are space saving
If you’re switching from a heat-only boiler to a combi; you’ll save tons of space because you can get rid of the hot water cylinder in your airing cupboard; and the cold water tanks in your loft.
This frees up storage space that you wouldn’t otherwise have had; and is appealing to smaller homes where space is at a premium.
You’ll also find plenty of boiler manufacturers who offer compact combi boilers that will even fit inside a kitchen cupboard!
Combi boilers are energy efficient
Thanks to the Boiler Plus Regulations, and improvements in our heating technology; all boilers are much more efficient than they used to be.
The Energy Saving Trust estimates says you can save £340 a year on your gas bill; by trading in an old-style non-condensing boiler; for a new condensing one.
But combi boilers may be more energy efficient in some cases compared to heat-only boilers.
Unlike heat-only boilers; combis heat water on demand, so you never pay to heat more water than you actually use.
With a heat-only boiler (which stores hot water), hot water tends to be produced twice a day; even if you don’t use it. If it doesn’t get used, this hot water cools down, wasting energy.
And as we mentioned above; if you have a heat-only boiler, you’ll also inevitably experience some heat loss from the hot water cylinder. Again, this is wasted energy, which is not an issue with a combi boiler.
Combi boilers never run out of hot water
If you’ve currently got a heat-only boiler; you might have had occasions where you’ve used all of the hot water in the cylinder; and have had to wait for it to refill.
This can be frustrating and can lead to family arguments over who used the last of it!
But this simply isn’t an issue with a combi. With no water cylinder to heat up, combi boilers can provide an unlimited supply of hot water on demand.
Since a combi heats water instantly when you turn on a tap, you’ll never run out of hot water again!
The drawbacks of installing a combi boiler
Whilst there are plenty of advantages to installing a combi, they’re not for everyone. Sometimes a new heat-only boiler or a new system boiler is a better choice.
Combi boilers struggle to meet high demands for hot water
It sounds counterintuitive to say that a combi will never run out of hot water; and then say that it can’t meet high demands for hot water – but stay with us!
A combi can’t run out of hot water because it heats it instantly when you turn on a tap. Unlike with a heat-only boiler, there is no cylinder that will eventually empty.
But because a combi heats the water instantly when you turn on a tap; it will struggle if you turn on multiple taps at the same time.
Most combi boilers provide between 9 – 16 litres per minute. Whatever the capacity, it will be halved if two hot water outlets are in use at the same time; i.e. to around 8 litres per minute at best.
This means that combi boilers are best suited to homes with relatively small hot water demands at any one time.
If people in your household all want to shower at the same time; a combi boiler may struggle to keep up with your demand.
In larger homes with multiple bathrooms, a heat-only or a system boiler would be a better choice.
You can read more about the pros and cons of combi boilers here.
What’s involved in replacing a heat-only boiler with a combi?
If you’ve decided that you want to switch to a combi, you may be wondering what’s involved. So, we’ve summarised the steps that The Heating People engineers will take:
Preparation
- Arrival of your engineer – when your heating engineer arrives to install your new boiler; they will discuss the planned work, to ensure that everyone is happy. They will explain where they will need access to, and for how long, so that you can plan your day.
- Preparation of the area – your engineer will put down floor coverings in all work areas and transit routes. So you can rest assured that your carpets will be protected from any debris.
- Draining the heating system – your engineer will need to drain your heating system before they can begin.
- Removal of your old existing boiler – your engineer will remove your old boiler; flue; cylinder and tanks; as well as any controls that won’t work with your new combi.
- Flush and clean – Depending on what was discussed during the quotation stage; your engineer will use the flushing method agreed upon. This ensures that your heating system is clean for your new boiler.
Installation
- Alteration of pipework – your engineer will alter your heating pipework to suit your new combi boiler. The Heating People only use quality products. We’ll only use copper or professional press fit systems, we don’t use DIY style push-fit systems.
- Routing of hot and cold pipework – your engineer will route your new hot and cold pipework from an existing point on your heating system; to your new boiler.
- Upgrading of the gas pipe – when changing to a combi boiler; it’s often necessary to upgrade the gas pipe to a larger one. This is because combi boilers require more power to heat the hot water. Where necessary, your engineer will do this.
- Installation of condensate pipe – If your old boiler was standard efficiency, your engineer will need to install a condensate pipe. This pipe will transfer the wastewater that gets produced by your new condensing boiler, into a sewer.
- Installation of the new boiler and the flue – your engineer will install your new boiler and flue. This is usually in the same position as your old boiler, but other locations are possible.
- Connection of the pipework – your engineer will connect all of the pipework to your new boiler.
- Wiring and controls – your engineer will complete the wiring and will install the controls for your new boiler.
- Safety checks – your engineer will conduct safety checks and commissioning checks for your new boiler.
Completion and handover
- Paperwork – your engineer will fill in all of the paperwork for your new boiler. They will fill out all commissioning test results in your benchmark log book.
- Tidy up – The Heating People will leave your home as clean and tidy as they found it! They will remove and dispose of your old boiler and any redundant parts.
- Handover – Your engineer will then complete a handover with you when all the work is complete. This ensures that you are as informed as possible on how to operate the boiler; how to use all the controls; and how to get the best efficiency from your system.
- Registration of your new boiler – After installing your new boiler, we register it with the manufacturers to activate its guarantee; and notify your local building control via the Gas Safe Register. We offer guarantees of up to 14 years on our boilers, for your peace of mind.
How long will it take to replace a heat-only boiler with a combi?
It generally takes 2-3 days on site to change from a heat-only to a combi boiler; depending on the work required.
How much will it cost to change from a heat-only boiler to a combi?
The price of replacing a boiler costs less than you might think. It obviously depends on what you are changing from, and what you are changing to.
But as a rough guide, at The Heating People:
- Replacing an existing combi boiler with a new combi boiler will cost between £1800-3000.
- Upgrading from a heat-only boiler to a combi boiler will cost between £2200-£3500.
- Swapping a heat-only boiler with a new heat-only boiler will cost between £1800-3000.
- Replacing a heat-only to a system boiler will cost between £1800-3000.
- Swapping a system boiler with a new system boiler will cost between £1800-3000.
Contact The Heating People today to arrange your free quotation.
Which combi boiler should I choose?
If you’ve decided that you want a combi boiler, your next challenge is deciding which one!
This can feel like a daunting task because there are so many manufacturers all offering extensive ranges of combi boilers in different sizes; with different key features and benefits.
Our best advice here is to choose an expert Gas Safe installer that you can trust. We’re going to make a bold claim here – your choice of installer is more important than your choice of boiler!
Many people take for granted the fact that your engineer is the number one contributor to your heating system’s efficiency. And as such, your engineer should be your first port of call in finding your perfect boiler.
The right engineer will calculate and recommend the best makes and models for your needs.
The Heating People conduct heat loss calculations as standard to correctly size your boiler. And will make recommendations on models that meet your requirements.
We only use products from manufacturers that offer outstanding engineering and reliability. Because of this, we can offer guarantees of up to 14 years on our boilers, for your peace of mind.
Final thoughts…
We hope you’ve found this guide useful in helping you to decide whether switching from a heat-only to a combi boiler sounds like a good option for you.
It ultimately depends on how you use your hot water at home.
If you have a large household that wants to use hot water simultaneously, a heat-only or system boiler will be your best option.
But if you don’t need to use multiple outlets at the same time, a combi could be a more efficient and space saving option.
For tailored advice, contact The Heating People to book your free survey.
You might also like to read our related blog: 6 Top Tips for buying a new boiler.
