Combi Boiler Prices UK & Installation Cost 2021

Whether you’re replacing an old boiler or installing a brand new one, a combination (combi) boiler will keep your house warm and energy efficient.


Condensing boilers get their name because they enter a “condensing mode” often, Basically, they start to extract heat from the exhaust gases that normally would be lost through the flue, in the process turning water vapour from the gas back into liquid water or condensate.

A condensing boiler captures much more (usable) heat from its fuel than a non-condensing boiler. In fact, The Energy Saving Trust (EST) suggest a condensing boiler can be up to 12% more efficient than a non-condensing boiler as it utilises the “latent heat” that is released from the burned fuel as it changes from vapour into water.

Having a better understanding of the combi-boiler prices in the market will help you better understand the expenses of new combi-boilers, including fitting, set up and servicing costs. In this guide will provide you useful information on the cheapest rates, laws and grants, oil combi boilers and popular combi boiler models such as Vaillant and vortex combi boilers.

What types of combination boiler are available?

Instantaneous: this used to be the most widely used combination boiler type and directly heats incoming mains cold water to supply your taps and all other hot water points.

Instantaneous condensing: Operates as an instantaneous boiler but saves more energy and has better and higher efficiencies than the standard combination boiler, this is the most commonly installed type now. In fact, exceptional circumstances aside, all new gas and oil central heating boilers fitted in the UK must now be condensing boilers by law.

Storage: This is an alternative to the Instantaneous combination boiler type mentioned above and is designed to give you better performance through the internal storage of heated water. The stored water also can give you an improved initial water supply from cold water mains on first turning on the tap. Once the stored heat has been used, this boiler will tend to operate as an instantaneous type.

Storage condensing: Operates in principle as a storage type but at higher efficiencies.

Combined Primary Storage Unit: This is a special category of storage combination which will incorporate a very large water store allowing a high water flow rate to taps and other draws off points and to quickly heat radiators before the water store is used.

The most popular type of combi boiler in the UK is the standard gas-fuelled model. These units don’t take nearly as long to heat homes as traditional system boilers do because you don’t need to store any hot water. This means you can get rid of the old water tank, which frees up space in the attic or airing cupboard.

You can purchase a gas fuelled combi boiler from three major sources:

    • A trusted plumbing or heating company in your local area, or an equally respected national business who specialise in providing new or replacement boilers. You can usually find trusted providers by talking to friends or relatives who have recently had boilers fitted or replaced. Or you can always contact a UK Tradesmen through us, most companies will be more than happy to provide a free quote for the cost of a gas combi boiler
    • Your existing energy supplier – such as British Gas or Npower, who can usually provide you with a new combi boiler quickly and with minimum fuss. We contacted both of these service providers and they provided us with the following quotes for standard quality, middle-of-the-range gas combi-boiler (prices still dependent on model):
    • You can also buy a gas combi boiler directly from the manufacturer or from retail outlets; shop around to secure the best deal.

These combi boiler units usually come with expert temperature controls and a standard instruction manual, and compared to old system boiler are extremely energy efficient.  So, even if the price of the new model itself doesn’t look that appealing, you are bound to end up saving on fuel costs on your energy bills within a matter of months.

Combi-boiler prices

Combi boiler prices can vary a lot depending on the size, brand and insurance/warranty. The EST reports that the average cost of a new gas boiler is around £2,300, including setup.  Below we present to you the most popular combi boiler prices in the market to help you get a good understanding of the price variations.

A Baxi combi-boilers cost between £568 – £1,200, when bought directly from the manufacturer.

A Vaillant combi-boiler from the manufacturer costs between  £796 – £1,400.

A Worcester Bosch combi-boiler purchased directly from the manufacturer costs £750 to £2,000.

The following table lists several of some of the most popular combi boiler prices:


Worcester Bosch Greenstar 42cdi Classic Typical Price – £1374
Worcester Bosch Greenstar 34cdi Classic Typical Price – £1,030
Vaillant ecoTEC Plus Combination Typical Price – £784
Potterton Promax Combi HE Plus Typical Price – £660
Potterton Performa Combi HE Typical Price -£650
Baxi Neta-Tec Plus Combi GA Typical Price -£640

Oil combi-boiler prices

Oil combi boilers prices are slightly higher and they also have more running expenses, but are a great choice in the event you don’t live close to the gas mains. Several oil combi-boiler prices can be seen below:


Model Price (including VAT)
Mistral 15/20 standard efficiency non-condensing combi boiler
 Mistral 15/20 high efficiency condensing combi boiler
Grant Vortex Pro 15/26 ERP kitchen/utility oil boiler  £1,828
Grant Vortex Blue 26 ERP internal boiler  £2,323
Firebird Enviromax C20HE slimline combi boiler White Cased  £2,492
Firebird Enviromax C100 high-efficiency commercial utility boiler  £4,017

Vaillant combi-boiler prices

According to their website, Vaillant is “Europe’s #1 Boiler Manufacturer” and they are offering “a 5-year guarantee on all Eco-Tec domestic boilers”. It sounds like a one-of-a-kind deal that is almost too good to be true! But what kind of combi boilers do Vaillant actually have to offer their customers?  Prices are usually dependent on a number of factors, including the Heat Output Rating of the combi boiler, its size and how much heat you will need for your home.

Ecotec Pro 28 Combi H – 720 mm
W – 440 mm
D – 335 mm
11.5 l/min 28 kW 86% – 90% £875.88
Ecotec Pro 24 Combi H – 720 mm
W – 440 mm
D – 335 mm
9.4 l/min 24 kW 86% – 90% £884.36
Ecotec Plus 824 Combi H – 720 mm
W – 440 mm
D – 335 mm
9.4 l/min 24 kW 86% – 90% £964
Ecotec Plus 831 Combi H – 720 mm
W – 440 mm
D – 335 mm
12.7 l/min 31 kW 86% – 90% £1060.88
Ecotec Plus Storage 937 Combi H – 720 mm
W – 440 mm
D – 597 mm
15.2 l/min 37 kW 86% – 90% £1205.65
Ecotec Exclusive 832 Combi H – 800 mm
W – 480 mm
D – 450 mm
12.9 l/min 32 kW 86% – 90% £1226.5
Ecotec Plus 837 Combi H – 720 mm
W – 440 mm
D – 403 mm
15.2 l/min 37 kW 86% – 90% £1273.92
Ecotec Exclusive 838 Combi H – 800 mm
W – 480 mm
D – 450 mm
15.2 l/min 38 kW 86% – 90% £1305

Cheapest combi-boiler prices

If you are a little worried about purchasing a second-hand boiler and would rather spend on the safe side, you can sometimes find great deals and extremely cheap combi boiler prices by avoiding the retailers altogether and going straight to the manufacturer. We compared three of the leading combi boiler brands to see who provides the cheapest prices when you go direct to the guys who make them:

    • Second-hand combi boilers – on seller sites such as eBay and PreLoved you can usually find a good combi boiler for somewhere between £300 and £700 – that’s less than half what you would pay when purchasing a new unit from most retailers
    • Recently reconditioned/refurbished combi boilers – users on similar sites also showcase recently reconditioned (akin to full service) combi boilers from around £600 to £900 – still a fair mark off full price models
    • Ex-showroom combi boilers – these can be purchased from many retailers and/or manufacturers for around £550 to £850 and at least come with the comforting knowledge that they are unlikely to have been used for more than thirty to fifty hours

Along with paying for your brand new (or new to you) combi-boiler, you will need to pay for professional combi boiler installation as:

    • It’s a legal requirement in the UK that everyone who installs, services or repairs gas appliances must be a Gas Safe registered engineer.
    • An experienced electrician to set up an electrical combi-boiler to BS 7671: 2008

Requirements for Electrical Installation

The EST recommends requesting references before employing a contractor and getting at least three estimates. If your boiler installer isn’t registered with any of these associations, you’ll need to self certify that the installation meets building regulations, which involves paying for a building inspector to check the installation.

Combi boiler installation costs will vary depending on which area of the state you live in and whether it will be installed on the same or different location

New combi boiler installation Approx cost for a mid-range boiler Time needed
Replacing an existing combi boiler
with a new boiler, in the same location
£1,995 1 day
Replacing an existing combi boiler
with a new boiler, in a new location
£2,550 1.5 days

Combi boiler servicing costs

It’s essential that you get your combi boiler serviced at least once a year to ensure that it’s operating safely and efficiently. A service will:

    • Detect any serious faults – saving you  money on future repairs and expensive emergency call-outs
    • Save your life – by detecting lethal Carbon Monoxide leaks and other dangerous defects
    • Reduce your fuel bills – by making sure your boiler runs at its most efficient
    • Stop you breaking the law – landlords are legally obliged to carry out annual boiler serviced in rental properties

Combi boiler annual servicing cost is between £60-£80.

Should I install a combi boiler?

Combi boilers are suitable for:

    • Combi boilers are suitable to be installed in small buildings that do not have the need for large amounts of hot water such as a one bathroom house or flat.

    • Small properties without large storage areas as a boiler will fit into a kitchen or laundry cupboard.

Combi boiler regulations

It’s vital that you comply with the following regulations when installing or changing a combi-boiler:

Condensing models – by the 1st of April 2005, part L of UK building regulations state that new boilers should be condensing models. This suggests that they recover more heat from waste gases than noncondensing versions and are therefore up to 12% more efficient, says the EST. There are a few very rare exceptions to this rule, for example when the boiler cannot be positioned safely, even if using an extended flue. In these examples, a capable engineer will provide you with a certificate to show that you need to establish a boiler instead

Planning permission – you won’t need planning permission to put in your new combi boiler if all of the work involved is internal. However, if your new boiler installation includes inserting a flue outside your home, or if you reside in a listed building, you need to seek advice from your local building power for advice before installing your combi-boiler

Building regulations – as of Oct 2010, building regulations stipulate that all new boilers should be A-rated or at least 88% efficient according to the Seasonal Performance of Domestic Boilers within the UK (SEDBUK) scale. SEDBUK has two rating methods, the 2005 one uses an A-G position (A being the most efficient rating) and the 2009 scale works in percentages. The EST says a new A-rated condensing boiler will save you up to £300 and 1,220kg of C02 each year, depending on what kind of boiler you’re replacing

Heating controls – Part L of building regulations requires you to truly fit proper heating handle systems when installing a fresh boiler. There are various types of controls to select from but you essentially require a programmable room thermostat to control the temperature and timing of the heating. Good managers can save 280kg and £55 of CO2 annually, reports the EST

Combi-boiler grants

combi-boiler-grantsYou may be eligible for a grant to help with the cost of installing or maintaining your combi-boiler from among the following outlets:

The Warm Front Scheme -This is really a government scheme for residents in England that is set to be eliminated in the next few years. You could be eligible for a grant of up to £3, 500 towards insulating and heating your home, if you have your home or privately rent.

The Scottish boiler scrapple scheme – The Scottish government has extended their boiler scrappage scheme whereby they supply GBP400 per family to the expense of replacing an old (commonly 1 over 10 years old) with a new Energy Saving Recommended boiler. Terms and conditions apply; consult the EST to discover if you’re qualified. Those on benefits and elderly Scottish residents are often able to get a grant through a municipality Energy Assistance Package.

Energy supplier grants – Carbon Emission Reduction Targets (CERT) require energy companies to help their customers make energy-saving home improvements. This may include providing discounts for new boiler installation. You’re eligible for grants from any energy company, not just the one who supplies energy to your home.

Local government grants – your local government or home improvement agency (HIA) may also provide grants towards the cost of heating and insulating your home.

Top Tips for Hiring a Quality Installer or Engineer

This list is certainly not exhaustive, but here are a handful of tips that will help you make the best and most informed decision when hiring a combi boiler installer:

    1. When installing a new combi boiler, make sure you hire an engineer who is registered with Gas Safe – this is a legal requirement in the UK.
    2. It is a good idea to talk to friends, family, and coworkers before deciding on an installer. They may be able to give you advice on a good company that worked well for them. Word-of-mouth is an excellent way to determine the reputation of a contractor or company, and if you mention the name of the person who recommended them, you may be able to negotiate a discount
    3. Hire someone registered with OFTEC if you’re installing an oil combi boiler; they specialise in installing and maintaining oil-fired boilers.
    4. Be sure the person you hired is a qualified electrician if you have gone with an electric combi boiler. They must also comply BS7671:2008 Requirements for Electrical Installations to safely fit an electric combi boiler.
    5. It is best to hire locally for the cheapest installation costs. While lesser-known companies may scare you, they are most likely the companies that have worked with homes in your area and therefore understand how to work with your property. They are also less likely to disappear than ‘cowboy contractors’, in the event you need a repair or have a complaint
    6. It may also be a good idea to check out several installation companies and hold preliminary interviews before hiring. This is particularly wise when going with local people, as they are most likely eager for work and don’t have the deep pockets to correct mistakes. Asking for additional information and chatting with the potential installers will enable you to build a working relationship and get a feel for the person.
    7. Whichever person or company you decide to go with, always ask for proof of that they have valid public liability insurance– this will cover you if anything goes wrong with the installation.

Take into consideration the above steps to ensure a more smooth, streamlined installation process all the way around.