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Best Combi Boiler 2020 – We reveal the Best in Class



How do I pick the best combi boiler for my home?

We throw out the boiler manufacturers' marketing blurb and consider what really matters: 1) the price, 2) the warranty length and 3) efficiency based on how 'low' the boiler can go (more on this below). As ever our guidance is completely impartial.

REMEMBER, a boiler is only as good as the installer that fits it. So that even technically 'the best' boiler will perform poorly in the home if it is not set up correctly. 99% of installers have not been trained to set up a condensing boiler correctly. You can access the 1% who can via our Elite Installer Network.

We have split results up according to price ranges so you can find the best combi boiler whatever your budget. The cream of the crop are as follows:

Best entry-level boiler winners:

Ravenheat HE80 

Best mid-range boiler winners are:

Intergas Xclusive and Vaillant Ecotec Plus

Best premium boiler winners are:

Viessmann Vitodens 200 and Worcester 8000


  1. How we judge our combi boilers
  2. Best combi boilers on a budget
  3. Best mid-range combi boilers
  4. Best premium range combi boilers
  5. Five steps to finding the best combi boiler
  6. The best combi boiler is only as good as your heating control
  7. Getting the best from your combi boiler
  8. Are combi boilers suitable for larger homes?

Top Combi Boilers

We present the top combi boilers in their class. We have selected the top-performing boilers that come with great all-round value for entry-level, mid-range and high-end budgets. We have found that the most expensive is not always the best! In each category there is a boiler to suit you. Some lesser-known brands have made it into the top 4 on their merits, but if you prefer a more familiar brand then you can choose from one of the others in the category.

1) Our judging criteria

We judge our boilers by a) value for money, b) warranty period and c) efficiency based on how low they can go.

a) Value for money - we consider the cost of the boiler against the warranty length and efficiency capacity. We have found some very reasonably priced boilers with better efficiency potential than more expensive models.

b) Warranty period - some manufacturers offer the same boiler with different warranty periods, for example 2 years or 7 years. The 7 year warranty model will be more expensive. We weigh up these packaged up boilers against other manufacturers of a similar price and cover.

c) How low they can go - all boilers operate within a range. For example 2-20kW or 8-30kW. The lower the boiler can go, for example 2kW in these examples, the more efficiently they can operate all year round. The average heat requirement for the majority of UK homes is 6-8kW on a very cold day. The boiler models with a lower output can operate efficiently during milder weather.

2) Best combi boilers on a budget

Budget boiler does not mean bad boiler! We have found four excellent, cost-effective options that offer very decent warranties and efficiencies for a low price. The lower the minimum output of the boiler the more efficiently it can operate all year round. The Ravenheat boiler outperforms some much more expensive models (not featured on this page of course, we only show the best of the best in class) with some more well known brands coming in just a little higher


Goes to Ravenheat HE80. Great price, great minimum output.


Goes to Alpha Evoke. Low price + 5 year warranty.


Is the Glow Worm Energy. Best warranty in the pack.

Rank Boiler Cupboard fit Boiler cost Manufacturer Cover Maximum output Minimum output Litres per minute hot water
1 Ravenheat HE80 Y £649 5 25kW 3.6kW 10.2
2 Alpha Evoke Y £700 5 25kW 4.3kW 12.1
3 Glow Worm Energy Y £700 7 19kW 5.0kW 12.1

3) Best mid-range combi boilers

The mid-range category is a big one with prices ranging from £780 to over £1,100 without any clear pattern in terms of performance or warranty. We have selected models with the lowest outputs combined with a great all-round package of aftersales care. Here is our pick of the best:


Goes to Intergas Xclusive. Great price, great minimum output.


Is the Vaillant Ecotec Plus. A 10 warranty from this familiar brand.


Is the Viessmann 100-W. Great all round package

Rank Boiler Cupboard fit Boiler cost Manufacturer Cover Maximum output Minimum output Litres per minute hot water
1 Intergas Xclusive 24 Y £969 10 19kW 3.6kW 10.1
2 Vaillant EcoTec Plus Y £1,145 10 21kW 3.8kW 10.5
4 Viessmann 100-W N £1,070 5-7 26kW 4.7kW 8.9

4) Best premium combi boilers

When prices go up we've made sure there is more value. Each of the boilers below comes with up to 10 years of warranty (NB some boilers must be fitted by an approved installer in order to qualify) plus some very low minimum outputs. Remember the lower the boiler can go, the more efficient it can be.


Goes to Viessmann Vitodens 200. Best minimum output on the market.


Goes to Worcester 8000. Low minimum output + 10 year warranty.


Is the Vaillant ecoTEC Green iQ. Low output plus 10 warranty from this familiar brand.


Is the Intergas Xtreme. Great all round package and low price

Rank Boiler Cupboard fit Boiler cost Manufacturer Cover Maximum output Minimum output Litres per minute hot water
1 Viessmann Vitoden 200-W N £1,602 2-5 25kW 1.9kW 15.7
2 Worcester Bosch 8000 30 N £1,275 5-10 30kW 3.0kW 12.3
3 Vaillant ecoTEC Green iQ N £1,651 5-10 24Kw 3.4kW 14.5
4 Intergas Xtreme N £1,268 7 30kW 3.6kW 13.3


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5) Steps to finding the best combi boiler for you

1) Low minimum output

All boilers operate in a range of outputs, for example, 2-20kW or 6-18kW. The lower the minimum output, the more efficiently the boiler can operate all year round. There are some great high efficiency boilers, often at great prices, from lesser-known brands such as Ravenheat and Intergas. Lower fuel bills are always a priority, as is warranty length and sometimes brand familiarity. We have put forward boilers with the lowest minimum outputs on the market so you can pick according to your other priorities.

2) Size your hot water requirements

Hot water performance is expressed in litres per minute (LPM) – this is how fast the boiler can heat cold water. The smaller boilers will always be around 10 litres per minute, the bigger boilers over 16 litres per minute. Litres per minute is important if you and your family have multiple bathrooms and shower at the same time in the mornings. The problem with combi boilers that give bigger hot water outputs is that they are too often oversized for the heating system - which is very inefficient. Don't worry, we have only featured boilers that can give a low minimum output alongside great hot water performance.

3) Do you need a cupboard fit?

If you are installing your new combi boiler in a kitchen cupboard you will need a compact boiler. However this are only available in the smaller models.

4) Is the warranty length important?

If you are moving in a few years perhaps you do not need one of the more expensive boilers with a 10 year warranty; a budget end boiler with 5 a year warranty will do and save you £500.

5) What is your budget?

There are some great value boilers even at the lower end. Work within your budget to find a boiler with the longest warranty.

6) The best combi boiler is only as good as the heating control

The efficiency of modern condensing boilers comes partly from their ability to operate at low outputs during warmer weathers, hence why a low minimum output is so important. When your home requires just 1-2kW of heat, as it often does, a boiler than can only go down a low 7kW is going to be oversized for much of the year. A boiler than can go down to 2kW will have the efficiency advantage.

However, in order for the boiler to reduce down to 2kW say it must be paired with a compatible control, known as a compensation control. These must speak the same language as the boiler. To find a compatible control for your high efficiency boiler see our Guide to advanced heating controls.

7) Getting the best from your combi boiler

The average UK home requires no more than 6-8kW of heat at peak times, i.e. on a cold day in February. Stated outputs for combi boilers are 24kW and upwards, which seem enormous. However these are for hot water production. For heating the output are lower but not by much, the smaller boilers start at 18kW which is still three times the size of most homes on a very cold day.

For combi boilers it is best to factor hot water production into your decision and just make sure the boiler, whichever one you pick, can be adjusted down (called range rating) to meet your heat requirement. This must be done by a competent gas safe registered engineer. Note however that really large combis will not adjust down low enough and will therefore prove very expensive to run. If you have multiple bathrooms in use at the same time opt for a system boiler with hot water cylinder.

For more on boiler sizing try our Guide to sizing your boiler. For more on the important role balancing and heating controls play in getting the most efficiency from your system, read our blog: Why oversized boilers are bad for your bank balance and the planet.

8) Are combi boilers suitable for larger homes?

Even a big combi can only do so much and the bigger you go the more the boiler is oversized the boiler can be for heating. If you have two or more bathrooms that are often in use simultaneously then you may want to consider a system boiler with hot water tank (assuming your water pressure is good enough). For more help with choosing the right boiler for a larger home, including the careful selection of a combi boiler, read our Guide to combis for larger homes.

Jo Alsop

Heating Hero

The Heating Hub

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