- Combi Boilers Explained
- Pricing & Installation
- Big Name Brands
The Ultimate Combi Boiler Guide
Want to know everything about Combi Boilers?
While an enthusiasm for expert knowledge of combi boilers is usually reserved for professional Gas Safe boiler engineers like the team at OneHeat, we don’t mind indulging your curiosity in these space and energy saving home-heating wonders with our Ultimate Combi Boiler guide.
Let’s get started!
The name Combi Boiler stands for combination boiler; a gas, LPG or electric appliance that produces hot water for both home-heating and hot taps on demand.
This differs from system, conventional or heat-only boilers in that it handles both the home’s requirements for hot water from the same unit.
Usually combi boilers are wall mounted, often compact enough to fit into a kitchen or bathroom cupboard or tucked away in a utility room, allowing households to not only save space when it comes to the boiler itself, but also because they don’t often require a hot water tank.
Their “heat on demand” design often means that combi boilers are the most economical boiler choice for most small to medium households, with the modern designs being both affordable and efficient when it comes to saving money on gas bills.
Combi Boilers work by using a heat source (usually gas supplied by the main gas grid but other units work on LPG or electricity) to pass heat through a heat exchanger and into the mains supplied water that runs through the boiler.
When somebody turns a ‘hot’ tap on at a sink or shower, or when the heating is turned on either manually or because a thermostat has noticed a drop in temperature, it creates a demand for the boiler.
In gas combi boilers, gas is then combusted in the combustion chamber creating heat. This heat is transferred to the water via the heat exchanger and then that hot water is delivered to where it needs to go in the house, either to the sink with the open tap, or to the radiators that are turned on throughout the house – simple
Of course, in a modern combi boiler things are a little more complicated than that, with plenty of modern technology to keep things more efficient such as condensing technology which draws residual heat from the flue to help keep things warm, and anti-frost technology to keep internal pipes clear and safe in Winter.
Combi boiler efficiency in modern units is often as high as 98% efficiency, meaning that a combi boiler could be the most efficient choice for your home, but a lot will depend on the size of your home and the usage.
Combi boilers are often most efficient when paired with a suitability sized home. Because most models rely on the mains water pressure to move water around the building, they can sometimes struggle to meet the demands of multiple taps and showers at the same time. Think about your home during the morning rush-hour: do you have several family members all using separate bathrooms at the same time? In which case, you may need either a more powerful combi boiler or consider looking at conventional boiler and water tank options.
That being said, combi boilers are the often the best and most efficient choice for most homes in the UK.
Most modern combi boilers are also compatible with remote and smart thermostats too. These clever devices range from simple programmable thermostats that monitor the temperature in the room they are placed and signal the combi boiler when things get too cold.
At the opposite end of the sophistication spectrum, advanced smart thermostats allow more complete control over the temperature in each room using smart TRVs, and remote operation so the boiler can be controlled via an app even when out of the house.
Used wisely, these tools can make a huge difference to the way your combi boiler uses gas, ensuring you can ensure your heating is used efficiency and you never have to heat an empty home.
What are the disadvantages of a combi boiler?
While a fantastic choice for most homes in the UK, a Combi boiler may be at a disadvantage in homes where peak hot water usage is particularly high, as there may be insufficient water pressure to cope with the demand of 2 or more bathrooms being used at the same time.
Because Combi boilers rely on mains water pressure, they can often be a little slow to pump hot water around later homes too, meaning you may have to run your tap for a little longer before it gets hot. Some models do have a small internal tank that allow for pre-heating, but these are usually on larger models.
Finally, if a combi boiler breaks down then the household is likely to lose both hot water AND heating, however with a modern combi boiler fitted well and service annually, this is pretty unlikely.
Some cheaper-end combi boilers may be picked up for as little as £800 and fitted for a few hundred more, but we can’t really recommend it in good conscience.
As with everything in life, you get what you pay for. By scratching around for truly barebones, no frills, rock-bottom boiler price you may have to sacrifice the quality of the combi boiler itself, or the quality of the installation and STILL lose out when it comes to needing maintenance and repairs more regularly, or wasting money on higher gas prices due to inefficient combustion.
In the worst cases, a cheaply fitted boiler may be unsafe. You should always have your boiler fitted and checked by a Gas Safe registered engineer. As an extra precaution, the team at OneHeat provide a free carbon monoxide detector for your peace of mind.
Moving into the category of affordable but well-performing boilers that will save you money, you can pick up a 24KW Glow Worm Compact for as little as £1695 or £15.50* per month on finance, including fitting by a Gas Safe registered engineer.
Larger and more top-end combi boilers may be fitted from upwards of £2500.
Where can I find Combi Boiler Prices?
OneHeat maintains a combi boiler price list on our website, features fixed prices subject to survey. If you would like a more tailored and accurate package putting together for you, you can book a callback with our team.
Can you get Combi Boiler Finance?
With OneHeat, you can spread the cost of your new boiler with our Combi Boiler finance options. We can offer boilers from just £15.50, and can often build a finance package for you that fits your budget.
We designed OneHeat so you can take advantage of expert boiler advice from our team, so book a call to be paired up with a suitable boiler and an affordable finance deal subject to status.
What is involved in a Combi boiler installation?
Installing a combi boiler is no issue for an experienced boiler engineer.
First, it’s important to survey the task, ensuring that it would indeed be cost-effective for a new boiler to be installed and the old one removed.
In many cases, a straight Combi-swap is required, where an old boiler will be removed and replaced by the new model in-situ.
Other jobs may require moving the location of the boiler in the house, including moving the associated pipes and flue.
This is why it is so important to carry out a good survey by a qualified person like those at OneHeat, allowing an adequately powered boiler to be suggested, and ensuring that there are no nasty surprises on installation day as all mains pipes and electrics are in place and in good working order.
With OneHeat, your combi boiler installation day will be chosen according to your diary and convenience, and is often as early as the next day!
Our engineer(s) will arrive when they are supposed to and begin by ensuring they have good, clear, clean and protected access to the boiler location. This is to ensure that nothing gets dropped, damaged or scuffed in the installation process. We want to ensure your home is adequately protected throughout.
From there, the correct tools will be laid out, the survey notes inspected and then work can commence, usually starting with the decommissioning of the old boiler and it’s removal from the property.
OneHeat has the correct waste disposal licensing to takes care of your old boiler and pipework where needed, so you don’t need to worry.
Once the area has been completely cleared of the old redundant system and the location for the new boiler has been made ready, installation can begin.
At OneHeat, most combi boiler installation will also include the fitting of an appropriate magnetic filter and limescale reducer – important for increasing the longevity of your whole heating system and the boiler.
Once everything is installed it can be safety tested and signed off. We will take care of registering the installation with Gas Safe and the manufacturer so the warranty can begin.
Finally, it’s tidy up time, and then your combi boiler installation is complete!
Combi Boiler Offers
Looking for the best Combi Boiler Offers? Not only does OneHeat have some of the lowest prices around including installation, but we throw in:
- FREE Magnetic Filter to protect against metallic debris
- FREE limescale reducer to reduce build ups in the pipework
- FREE carbon monoxide detector for safety and peace of mind.
What Are The Best Combi Boiler Brands?
At OneHeat we find that any of these Combi Boiler brands will give you years of reliable and cost-effective hot water and heating.
Worcester Bosch Combi Boilers
Looking for style as well as fuel-efficient functionality? Check out our range of stunning Worcester Bosch Combi Boilers
Vaillant Combi Boilers
Vaillants range of combi boilers are often regarded as best in class. You may pay a little more now, but you’re buying long-lasting performance.
Glow Worm Combi Boilers
At the cost-effective end of the combi boiler spectrum, Glow Worm combi boilers are A-Rated units at budget prices.
Ideal Heating Boilers
Some of the best combi boilers for smaller homes for those looking to maximise performance from a smaller budget
ATAG Combi Boilers
Towards the big, beautiful and premium range of combi boilers, ATAG are powerful yet efficient for their size
Combi Boiler FAQs
While there is no plan to ban combi boilers as a concept, there is an upcoming phase-out of gas boilers.
UK laws are already in place that mean any new homes built from 2025 will not be fitted with a gas combi boiler.
The whole point of a combi boiler is to delivery hot water to where it is needed without the need for a hot water cylinder or tank, however yes, it is possible and potentially suitable to deploy a hot water tank into a system with a combi. If you believe you may require such as set up, book a FREE survey with our Gas Safe engineers by calling 0800 321 3438
The best combi boiler is the one that suits the unique needs of your home for the best price and with reliable, long-term performance, and so the best combi boiler will be different in every home.
You need to take your budget into consideration (including how much a new boiler may save you on your gas bill) as well as how many bathrooms, showers, baths and sinks you have, and how heavily they are used at peak times.
That being said, we’re very proud of the range of combi boilers on offer through OneHeat, and feel confident there should be at least a few fantastic options to fit your budget.
We recommend that any combi boiler running from the mains water supply in the UK should also have a magnetic filter installed. In fact, we throw an appropriate magnetic filter in for free with every new boiler purchase.
Without a magnetic filter, your boiler and the pipes that feed your central heating system can become damaged over time, and many manufacturer’s warranties and guarantees are only valid if you have a filter installed too.
At OneHeat, we also believe that central heating systems benefit from limescale reducers, and also fit those free of charge with each boiler purchase.
A combi boiler does hot water AND heating, but unless you live in practically arctic conditions, keeping the heating on full time isn’t generally recommended.
Most homes can save money with a new combi boiler if it is ran efficiently. Many people choose to take advantage of the programable timers built into modern combi boilers, having the heating turn on just before they are due to get up for work, and turn off just before bed where the a duvet takes over.
Of course, when things get cold in Winter, you may choose to set a minimum temperature on your thermostat so that the combi boiler turns on and heats your home if it drops below a certain temperature. Done properly, this can help save you money.
If you’re not using your heating at all in the summer months, simply flip the combi boiler onto hot-water-only mode, usually just by turning a dial – easy!
The lifespan of a modern combi boiler is usually about 10 years providing that it is serviced annually and a filter is fitted.
