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Combi Boiler Guide: Prices, Sizes, Types and and Leading Brands

Combi boilers are the most popular type or boiler in the UK due to their excellent efficiency and space-saving design.

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When it comes to the cost of a new combi boiler, prices vary greatly according to the brand, output and warranty. The average cost of a combi boiler ranges from £455 to over £2,650, but you’ll need to pay an extra £600 to £1,500 to get the boiler installed. Combine these figures, and you’re looking at spending anything from £1,055 to £4,150 for a new combi and the installation.

Before choosing a combi boiler for your home, you need to know what size (kW output) and type of combi boiler you require. You must also consider your budget, which is why it’s so important to compare combi boiler prices and familiarise yourself with each of the available boiler brands.

To help you make the right decision, we’ve put together a guide that explains what a combi boiler is, how to select the right size for your home and the different fuel types that the boiler run on. Our useful guide also lets you compare combi boiler prices and the pros and cons of installing a new combination boiler.

What is Combi Boiler?

A combi (or combination) boiler provides not only heat for your radiators but also instant hot water for your taps. As all combi boilers heat water directly from the mains and do not require a separate hot water storage cylinder in the airing cupboard or cold water storage tank in the loft, they are perfect for flats and smaller properties with limited indoor space. Due to their ability to heat water instantly on demand, combi boilers are also more economical and energy-efficient.

The Right Size Combi Boiler For Your Home

Choosing a new combi boiler can be overwhelming, with so many options available in the UK today. Although it’s impossible to tell you which size combi you will need without assessing your property and usage habits, we have put together a rough guide below to help find the right size boiler.   

PROPERTY SIZEBEDROOMSBATHROOMSRADIATORSIDEAL OUTPUT
Flat or small house1-21Up to 10 24-27kW
Medium house 3-41-2Up to 15 28-34kW
Large house4+2-3 Up to 20 35-42kW

Please note: This information must be used as a rough guide only and won’t be accurate for every property. We suggest you always consult a Gas Safe engineer to give you advice on the best boiler type, model and size for your home.

Combi Boiler Types

Most people opt for gas combi boilers as they tend to be cheaper to run, however, there are other options to consider before making any decisions. Let’s take a look at the different types of combi boilers from which you can choose.

Gas Combi Boilers

As previously mentioned, natural gas combi boilers are the most common option for properties connected to the mains gas supply because it costs less to heat a home with gas than with oil or electric.

Oil Combi Boilers

If you are off the gas grid, you may want an oil-fired combi boiler. You will need a separate tank (outside) to store the oil, which is delivered to your home by an oil supplier. This means you must keep an eye on how much oil you are using to make sure you never run out before your next delivery is due.

LPG Combi Boilers

LPG (which stands for liquefied petroleum gas) combi boilers are similar to oil boilers in that the fuel needs to be delivered by a supplier and then stored in an outdoor tank. Again, like oil boilers, they burn fuel to produce the energy that provides you with hot water for your taps and radiators. You may be interested to know that some natural gas combi boilers can be converted to LPG boilers with special conversion kits.

Electric Combi Boilers

Another option if do not have access to mains gas is electric combi boilers, which use electricity to heat water rather than gas. One of the biggest selling points of these boilers is that they can be up to 99% efficient. These boilers are also compact and allow for greater siting flexibility because they do not require a flue. The downside is that running costs may be higher as electricity is more expensive than gas.

Combi Boiler Advantages and Disadvantages

Even though combi boilers have many advantages and are common in homes across the UK, they may not be right for every property. It is therefore essential that you seek advice from a Gas Safe registered engineer before purchasing a new boiler, regardless of type.

Advantages

Compact size: The majority of combi boilers are extremely compact and can be installed almost anywhere in the home. Some are even small enough to fit inside a standard-sized kitchen cupboard. Plus, you won’t need a cold water tank or hot water cylinder with a combi, which means more free space in your loft and airing cupboard.

Hot water on demand: Combi boilers are designed to provide hot water (and central heating) on demand from one single unit, so you don’t need to wait for the water to heat up whenever you decide to have a bath or shower. Also, combi boilers are more cost-effective because they only heat the water you use.

Shorter installation time: With less pipework and no extra tanks to deal with, combi boilers are relatively easy to install. This means you can expect a quicker and neater installation, which helps to keep fitting costs to a minimum as well.

You save money: As water is heated instantly (rather than being heated and then stored in a separate cylinder), combi boilers are more energy efficient and have a smaller carbon footprint when compared to conventional boilers. New combi boilers are also condensing boilers, meaning they save energy by reusing heat that would otherwise be wasted. By being so efficient, combi boilers can help to lower your energy bills.

Disadvantages

Not great for homes with multiple bathrooms: Combi boilers are best suited to smaller properties and households with lower hot water demands. Remember, they do not work alongside a tank or cylinder, so they may struggle to cope with two baths or showers running at the same time. Because of this, combi boilers are generally not recommended for homes with more than one bathroom.

No backup immersion heater: In the event of a breakdown, you may be left without any hot water as combi boilers are not fitted with immersion heaters. You can, of course, call out an engineer but there is no guarantee that they will be able to come to your home and fix the problem right away.

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Combi Boiler Prices By the Leading Brands

Many brands, such as Worcester Bosch, Viessmann and Ideal manufacture combi boilers, which vary in size and cost depending on the model. There are lots of options to choose between including budget, mid-range and high-end models. Obviously, the larger and more sophisticated the combi boiler, the more you will need to pay.

Below are some comparison tables that enable you to compare combi boiler prices and models from different boiler brands to give you a better idea of prices. The prices listed include VAT but exclude the cost of installation.

Worcester Bosch

MODELDIMENSIONSOUTPUTMAX FLOW RATEFFICIENCY TYPICAL PRICE
Greenstar 28 CDi Compact Combi H - 680 mm
W - 390 mm
D - 280 mm
28 kw11.4 l/min £ 1,105.04
Greenstar 30 Si Compact Combi H - 690 mm
W - 390 mm
D
- 280 mm
30 kw 12.3 l/min £ 1,142.46
Greenstar 24i Junior CombiH - 710 mm
W - 400 mm
D - 300 mm
24 kw 9.8 l/min £ 1,169.99
Greenstar 38 CDi Classic Combi H - 760 mm
W - 440 mm
D - 360 mm
38 kw 16.4 l/min £ 1,427.92
Greenstar 38 CDi Classic Combi H - 850 mm
W - 600 mm
D - 600 mm
29 kw 20.1 l/min £ 2,053.68
Greenstar Heatslave II 32 H - 855 mm
W - 520 mm
D - 600 mm
32 kw 22 l/min £ 2,520.00
Greenstar Heatslave II 25 ExternalH - 950 mm
W - 640 mm
D - 770 mm
25 kw 18 l/min £ 2,572.82

Ideal

MODELDIMENSIONSOUTPUTMAX FLOW RATEFFICIENCY TYPICAL PRICE
Independent C24 Combi H - 700 mm
W - 395 mm
D - 278 mm
24 kw9.9 l/min £ 625.36
Logic Combi 24 H - 700 mm
W - 395 mm
D - 278 mm
24 kw9.9 l/min £ 718.38
Logic + Combi 35H - 700 mm
W - 395 mm
D - 278 mm
35 kw14.5 l/min £ 914.75
Vogue Combi 26H - 740 mm
W - 445 mm
D - 330 mm
26 kw10.6 l/min £ 980.00
Logic Max Combi 35 H - 700 mm
W - 395 mm
D - 278 mm
35 kw14.5 l/min £ 1,077.43
Vogue Max Combi 40H - 700 mm
W - 395 mm
D - 278 mm
40 kw16.4 l/min £ 1,339.20

Biasi

MODELDIMENSIONSOUTPUTMAX FLOW RATEFFICIENCY TYPICAL PRICE
Riva Plus Combi ERP 24H - 803 mm
W - 400 mm
D - 350 mm
24 kw11.6 l/min £ 454.80
Advance Plus Combi ERP 30 H - 700 mm
W - 400 mm
D - 290 mm
30 kw16.2 l/min £ 598.90
Inovia Combi ERP 30 H - 700 mm
W - 400 mm
D - 290 mm
30 kw16.2 l/min £ 660.00
Advance Combi 35H - 700 mm
W - 400 mm
D - 290 mm
35 kw13.3 l/min £ 673.50

Vokera

MODELDIMENSIONSOUTPUTMAX FLOW RATEFFICIENCY TYPICAL PRICE
Compact A 29 H - 715 mm
W - 405 mm
D - 248 mm
29 kw11.9 l/min £ 485.00
Vision Combi 30 H - 715 mm
W - 405 mm
D - 248 mm
30 kw12 l/min £ 590.00
Evolve Combi 28 H - 750 mm
W - 420 mm
D - 275 mm
28 kw12.3 l/min £ 775.00
Unica i Combi 36H - 780 mm
W - 400 mm
D - 358 mm
36 kw14.7 l/min £ 885.00
Linea 1 Combi 38 H - 845 mm
W - 453 mm
D - 358 mm
38 kw15.6 l/min £ 1,069.99

Keston

MODELDIMENSIONSOUTPUTMAX FLOW RATEFFICIENCY TYPICAL PRICE
Keston Combi 35 H - 700 mm
W - 395 mm
D - 278 mm
35 kw14.5 l/min £ 1,303.70

Ferroli

MODELDIMENSIONSOUTPUTMAX FLOW RATEFFICIENCY TYPICAL PRICE
Ferroli i29 CombiH - 680 mm
W - 400 mm
D - 330 mm
29 kw15.6 l/min£ 429.00
Modena 32C HE Combi H - 600 mm
W - 400 mm
D - 320 mm
32 kw13.1 l/min £ 646.16

Viessmann

MODELDIMENSIONSOUTPUTMAX FLOW RATEFFICIENCY TYPICAL PRICE
Vitodens 050-W 35 CombiH - 707 mm
W - 400 mm
D - 350 mm
35 kw14 l/min £ 874.80
Vitodens 100-W 26 Combi H - 700 mm
W - 400 mm
D - 350 mm
26 kw10.6 l/min £ 1,114.88
Vitodens 200-W 30 Combi H - 850 mm
W - 450 mm
D - 360 mm
30 kw14.3 l/min £ 1,594.34
Vitodens 111-W 35 Storage CombiH - 900 mm
W - 600 mm
D - 480 mm
35 kw18 l/min £ 1,735.78
Vitodens 222-F 26 CombiH - 1425 mm
W - 600 mm
D - 595 mm
26 kw23 l/min £ 2,686.85

Vaillant

MODELDIMENSIONSOUTPUTMAX FLOW RATEFFICIENCY TYPICAL PRICE
ecoFIT Pure Combi 25H - 700 mm
W - 390 mm
D - 295 mm
25 kw10.4 l/min £ 858.00
ecoTEC Pro Combi 28H - 720 mm
W - 440 mm
D - 338 mm
28 kw11.1 l/min £ 925.00
ecoTEC Plus Combi 32H - 720 mm
W - 440 mm
D - 338 mm
32 kw13 l/min £ 1,185.65
ecoTEC Exclusive Combi 43H - 720 mm
W - 440 mm
D - 474 mm
43 kw17.8 l/min £ 1,916.88

Baxi

MODELDIMENSIONSOUTPUTMAX FLOW RATEFFICIENCY TYPICAL PRICE
100 Combi LPG 24H - 700 mm
W - 395 mm
D - 300 mm
24 kw9.8 l/min£ 608.40
400 Combi 24H - 700 mm
W - 395 mm
D - 279 mm
24 kw9.8 l/min £ 689.44
200 Combi 28H - 700 mm
W - 395 mm
D - 279 mm
28 kw11.5 l/min£ 698.00
100 Combi 28H - 700 mm
W - 290 mm
D - 300 mm
28 kw11.5 l/min£ 728.40
400 Combi LPG 28H - 700 mm
W - 395 mm
D - 279 mm
28 kw11.5 l/min £ 729.41
600 Combi 30H - 700 mm
W - 390 mm
D - 285 mm
30 kw12.2 l/min £ 808.61
Duo-tec Combi 33H - 780 mm
W - 450 mm
D - 345 mm
33 kw13.5 l/min £ 918.04
EcoBlue + Combi 33H - 700 mm
W - 390 mm
D - 295 mm
33 kw13.5 l/min £ 995.76
Platinum Combi 40H - 780 mm
W - 450 mm
D - 345 mm
40 kw16.4 l/min £ 1,126.67
EcoBlue Advance Combi 40H - 763 mm
W - 450 mm
D - 345 mm
40 kw16.4 l/min £ 1,228.72

Potterton

MODELDIMENSIONSOUTPUTMAX FLOW RATEFFICIENCY TYPICAL PRICE
Gold Combi 28H - 780 mm
W - 450 mm
D - 345 mm
28 kw11.5 l/min£ 696.28
Titanium Combi 24H - 780 mm
W - 450 mm
D - 345 mm
24 kw9.8 l/min £ 767.52
Assure Combi 25H - 700 mm
W - 290 mm
D - 345 mm
25 kw10.2 l/min£ 834.00
Promax Combi 28H - 780 mm
W - 450 mm
D - 345 mm
28 kw11.5 l/min£ 968.33
Promax Ultra Combi 40H - 763 mm
W - 450 mm
D - 355 mm
40 kw16.4 l/min £ 1,309.80

Glow-Worm

MODELDIMENSIONSOUTPUTMAX FLOW RATEFFICIENCY TYPICAL PRICE
Easicom3 Combi 24H - 740 mm
W - 418 mm
D - 300 mm
24 kw9.8 l/min£ 580.00
Betacom3 Combi 30H - 740 mm
W - 418 mm
D - 300 mm
30 kw9.8 l/min £ 610.00
Essential Combi 28H - 740 mm
W - 418 mm
D - 300 mm
28 kw11.5 l/min£ 658.00
Ultimate3 Combi 35H - 740 mm
W - 418 mm
D - 300 mm
35 kw11.5 l/min£ 774.00
Energy Combi 35H - 700 mm
W - 390 mm
D - 280 mm
35 kw11.5 l/min £ 912.24
Energy Store Combi 35H - 890 mm
W - 470 mm
D - 561 mm
35 kw12.2 l/min £ 1,547.64

Alpha

MODELDIMENSIONSOUTPUTMAX FLOW RATEFFICIENCY TYPICAL PRICE
Evoke Combi 28H - 712 mm
W - 440 mm
D - 255 mm
28 kw12.1 l/min£ 625.00
E Tec Combi 33H - 712 mm
W - 440 mm
D - 255 mm
33 kw14.1 l/min£ 729.00
E Tec Plus Combi 28H - 712 mm
W - 440 mm
D - 268 mm
28 kw12.1 l/min£ 838.13
Intec GS Combi 40H - 1000 mm
W - 440 mm
D - 360 mm
40 kw15.8 l/min£ 1,795.00

Ariston

MODELDIMENSIONSOUTPUTMAX FLOW RATEFFICIENCY TYPICAL PRICE
Clas HE 30 Evo CombiH - 810 mm
W - 490 mm
D - 420 mm
30 kw12.9 l/min£ 659.00
Clas Net One 38 CombiH - 745 mm
W - 400 mm
D - 385 mm
38 kw15.5 l/min£ 1,140.00

Don’t forget: Prior to making any decisions, you must ask a Gas Safe engineer to help you determine which combi boiler model and output is right for your home.

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