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Use our quick boiler size calculator tables

24/02/2020

 

How can I work out what size boiler I need?

Use our simple tables to calculate what size boiler you need and then find the best boiler in your size range. The right sized boiler is smaller than you think. We routinely oversize our boilers in the UK which contributes to lower efficiencies and shorter lifespans. Why does this happen? 99% of installers have not been trained to specify and setup condensing boilers correctly. For more on our work to expose and correct the industry failings read our Heating Heroes page.

In this guide we help you work out your heat requirements based on property size and age and review boiler models. Sizing a combi boiler is a bit more complicated as the output needed for hot water is much larger, but we offer help there too.

Overview of boiler sizing

The correct size boiler is like car cruising on a motorway

There is often a temptation to oversize the boiler, just in case. Oversizing is very inefficient and accelerates wear and tear which can cost thousands over the lifetime of the boiler in higher fuel bills and early replacement.

Think of a boiler like a car. A car is at its most efficient traveling on a motorway for long periods. The same principle applies to boilers. A boiler is at its most efficient when it can run for long periods and to do this it must be accurately set at the same kW output required to heat your home.

Oversized boilers will ‘cycle’ on and off, as the boiler heats up too quickly, runs for short blasts and then turns off. Like the clutch of a car stuck in town centre traffic, the stop-start cycles will use more fuel and put the components under greater stress than when cruising along a motorway.

Calculating your boiler size - it's smaller than you think!

If you have a system or regular boiler the size will be based on the heat requirements of your property. For combi boilers, the size is ‘bigger’ because it includes hot water production.

As a guide, the vast majority of homes in the UK have a heat requirement of under 10kW, commonly 6-8kW. For system and heat-only boilers, this is easy to accommodate as smaller boilers are available.

For combis however the heating output tends to be around 18kW for the heating side of the system and 24kW and upwards for hot water. The good news is most modern boilers can be 'range rated' down, i.e. your installer can adjust the output of the boiler to 6-10kW to accurately meet your maximum heat requirement. Make sure you ask your installer to do this.

Impact on boiler efficiency

Condensing boilers boast efficiencies of 90% or more but the upspoken truth is they almost never reach their factory stated efficiencies in practice because 99% of installers have not be trained in condensing technology. Actual efficiencies are closer to 80%. The reasons behind this are many and concern how the boiler is sized, its minimum output, the heating control that is used and whether the radiators stay balanced. We have produced a very easy step by step guide to getting the most from your condensing boiler in our blog Why condensing boilers do not condense.

1) Sizing a combi boiler

On the table below, find your property’s age across the top and its size down the left-hand column. Property ages assume standard insulation measures, such as double glazing and loft insulation have been retrofitted or - for newer properties - were installed at the time of construction. Some older properties have been very well insulated retrospectively. If your levels of insulation are very high for the property’s age, then you may wish to move a column to the right. If you are planning on adding bathrooms you will need to factor in hot water flow rates (see below).

REMEMBER, the average UK home has a maximum heat requirement of 6-8kW on a very cold day, according boiler manufacturer Viessmann, very properties exceed 10kW. You can buy a bigger boiler but your installer must reduce the output down on installation.

Sizing for hot water

The hot water flow rate of a combi boiler - expressed as ‘litres per minute’ (LPM) - indicates how quickly a combi boiler can heat hot water. Hot water flow rates vary from 9.8 LPM to 25 LPM! For houses with multiple bathrooms, the hot water flow rate will be halved if two showers are running simultaneously so it’s important to look at the flow rates. If you have multiple bathrooms you may wish to consider a boiler with a higher flow rate. NB for multiple bathroom properties it is really much better to use a system boiler and hot water tank.

Combi Boilers

Age of property pre 1900 1920s-1930s 1950-1980s 1990s 2000 onwards
Insulation levels Poorly insulated Some insulation Moderately insulated Reasonably insulated Well insulated
No of bedrooms and bathrooms          
1 bed + 1 bath 7kW/9-12LPM 7kW/9-12LPM 6kW/9-12LPM 6kW/9-12LPM 4kW/9-12LPM
2 bed + 1 bath 8kW/9-12LPM 8kW/9-12LPM 7kW/9-12LPM 6kW/9-12LPM 5kW/9-12LPM
2 bed + 2 bath 8kW/12-16LPM 8kW/12-16LPM 7kW/12-16LPM 6kW/12-16LPM 5kW/12-16LPM
3 bed + 1 bath 9kW/9-12LPM 9kW/9-12LPM 8kW/9-12LPM 7kW/9-12LPM 6kW/9-12LPM
3 bed + 2 bath 9kW/12-16LPM 9kW/12-16LPM 8kW/12-16LPM 7kW/12-16LPM 6kW/12-16LPM
4 bed + 1 bath 10kW/9-12LPM 10kW/9-12LPM 9kW/9-12LPM 8kW/9-12LPM 7kW/9-12LPM
4 bed + 2 bath 10kW/12-16LPM 10kW/12-16LPM 9kW/12-16LPM 8kW/12-16LPM 7kW/12-16LPM
5 bed + 2 bath 14kW/12-16LPM 12kW/12-16LPM 10kW/12-16LPM 10kW/12-16LPM 9kW/12-16LPM
5+ bed + 2 bath 16kW/12-16LPM 15kW/12-16LPM 14kW/12-16LPM 12kW/12-16LPM 10kW/12-16LPM

 

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Combi boilers according to brand and budget:

Remember the kW outputs for combis appear bigger because they are sized for hot water. We have grouped boilers together based on the heating output and on that basis the smallest of combi boilers will heat most homes. Look down the LPM column to determine hot water production and REMEMBER to ask your installer to range rate (reduce) the kW output down to meet your actual heat requirement. Also remember that most big combis are not suitable even for a large house. We have shown them here because they give good hot water production, but a 40kW heating boiler could heat a mansion! Its output must be reduced or better still consider a system boiler with priority hot water set up.

 

18-19kW boilers / 9.6-12.1 litres per minute

Manufacturer/Model Code Price Heating output (Size) Litres per minute for hot water Standard warranty Free Extended Warranty Min Heating Output
Glow Worm Energy 25kW £700 18kW 12.1 2 2 5.3kW
Ideal Vogue C26 £1,056 18kW 10.6 10 10 4.0kW
Vaillant EcoFIT Pure 825 £865 18kW 12.1 2 7 5.3kW
Vaillant EcoTEC Pro 24 £942 19kW 9.6 2 7 9.6kW
Vaillant EcoTEC Plus 825 £1,107 19kW 10.5 5 10 3.8kW
Vaillant EcoTEC Pro 28 £984 19kW 11.1 2 7 9.6kW

 

20-22kW boilers / 9.8-12.4 litres per minute

Manufacturer/Model Code Price Heating output (Size) Litres per minute for hot water Standard warranty Free Extended Warranty Min Heating Output
Baxi/Duotec 24 £750 21kW 9.8 7 7 7.4kW
Potterton Titanium 24 £715 20kW 9.8 7 7 7.4kW
Baxi Eco Blue Advance 24 £1,020 20kW 9.8 7 7 4.9kW
Potterton Promax 24 Plus £833 20kW 9.8 2 2 7.4kW
Baxi 200 224 £620

22kW

9.8 3 3 5.2kW
Baxi 400 424 £670 22kW 9.8 3 3 5.2kW
Glow Worm Easicom 24 £520 20kW 10 2 4 5.3kW
Baxi 200 228 £620

22kW

11.5 5 5 5.2kW
Baxi 400 428 £699 22kW 11.5 5 5 5.2kW
Viessmann/Vitodens 050 29kW £735 >22kW 12.4 3 7 5.9kW
Ravenheat HE80 £649 21kW 10.2 5 5 3.6kW
Worcester Greenstar 2000 25 £780 20kW 10.0 5 10 4.8kW
Intergas Xtreme 24 £1,209 20kW 11.0 7 7 3.6kW

 

24-26kW boilers / 9.8-16.5 litres per minute

Manufacturer/Model Code Price Heating output (Size) Litres per minute for hot water Standard warranty Free Extended Warranty Min Heating Output
Worcestster Bosch Greenstar Si 25Si £1,045 24kW 9.8 5 10 8.1kW
Ideal Logic+ C24 £825 24kW 9.9 7 7 7.1kW
Viessmann Vitodens 100 26kW £1,070 24kW 8.9 5 10 4.7kW
Baxi Platinum 24 £1,110 24kW 9.8 10 10 7.4kW
Ideal Independent C24 £670 24kW 9.9 5 5 4.8kW
Ideal Independent C30 £745 24kW 12.3 5 5 6.1kW
Glow Worm Easicom 28 £550 24kW 11.7 2 4 6.3kW
Ideal Independent C35 £805 24kW 14.5 5 5 7.1kW
Baxi Duotec 28 £885 24kW 11.5 7 7 9.5kW
Potterton Titanium 28 £790 24kW 11.5 7 7 9.5kW
Worcester Bosch Si 30Si £1,170 24kW 11.5 5 10 7.0kW
Baxi Eco Blue Advance 28 £1,170 25kW 11.5 7 7 6.0kW
Vaillant EcoTEC {ro 30 £1,160 30kW 12.3 2 7 6.2kW
Ideal Logic+ Combi C30 £890 24kW 12.4 7 7 6.1kW
Ideal Logic+ Combi C35 £1,035 24kW 14.5 7 7 7.1kW
Baxi Ecoblue Advance 28 £1,170 25kW 11.5 10 10 6.0kW
Vaillant EcoTEC Plus 832 £1,290 24kW 11.5 5 10 5.2kW
Glow Worm Easicom 28 £550 25kW 11.7 3 3 6.3kW
Glow Worm Energy 30kW £800 25kW 12.5 2 2 6.3kW
Glow Worm Energy 35kW £900 25kW 14.4 2 2 7.2kW
Potterton Promax 28 Plus £877 25kW 11.5 2 2 9.5kW
Vaillant EcoFIT Pure 830 £1,110 25kW 14.2 2 7 6.3kW
Vaillant EcoFIT Pure 835 £1,140 25kW 16.5 2 7 7.5kW
Vaillant EcoTEC Green iQ 835 £1,651 25kW 14.5 5 10 3.4kW
Ideal Vogue C32 £1,115 26kW 13.1 10 10 4.6kW
Main Eco Elite 25 £525 26kW 10.1 5 5 8.4kW
Viessmann Vitodens 200 26kW £1,020 26kW 10.7 3 10 1.9kW
Ravenheat HE 98S £719 26kW 12.1 5 5 3.7kW
Intergas Xtreme 30 £1,268 26kW 13.3 7 7 3.6kW

 

28-29kW boilers / 11.2 - 15.9 litres per minutes

Manufacturer/Model Code Price Heating output (Size) Litres per minute for hot water Standard warranty Free Extended Warranty Min Heating Output
Viessmann Vitodens 100 30kW £1,115 27kW 11.2 5 10 5.4kW
Ferroli Modena 32kW £670 28kW 13.1 5 5 7.2kW
Baxi Duotec 33 £990 28kW 13.5 7 7 10.2kW
Potterton Titanium 33 £855 28kW 13.5 7 7 10.2kW
Baxi Platinum 28 £1,010 28kW 11.5 10 10 9.5kW
Baxi Ecoblue Advance 33 £1,300 28kW 13.5 10 10 7.1kW
Potterton Promax 33 Plus £1,045 29kW 13.5 2 2 10.2kW
Vaillant EcoTEC Plus 838 £1,440 29kW 15.9 5 10 6.5kW

 

30kW boilers / 11 - 15 litres per minute

Manufacturer/Model Code Price Heating output (Size) Litres per minute for hot water Standard warranty Free Extended Warranty Min Heating Output
Viessmann Vitodens 200 30kW £1,602 30kW 12.3 3 10 1.9kW
Main Eco Elite 30 £570 30kW 12.3 5 5 9.4kW
Viessmann Vitodens 50 35kW £855 30kW 14.5 3 7 8kW
Vaillant EcoTEC Plus 835 £1,470 30kW 14.3 5 10 5.8kW
Worcester Greenstar 2000 30 £740 30kW 12.0 5 10 4.8kW
Worcester Greenstar 8000 30 £1,275 30kW 12.3 5 10 3.0kW
               

 

32-34kW boilers / 13.5 - 16.4 litres per minutes

Manufacturer/Model Code Price Heating output (Size) Litres per minute for hot water Standard warranty Free Extended Warranty Min Heating Output
Baxi Duotec 40 £1,045 32kW 16.4 7 7 12.1kW
Potterton Titanium 40 £930 32kW 16.4 7 7 12.1kW
Viessmann Vitodens 100 35kW £1,090 32kW 13.5 5 10 5.4kW
Ideal Vogue C40 £1,225 32kW 16.4 10 10 5.7kW
Baxi Platinum 33 £1,145 33kW 13.5 10 10 10.2kW
Ferroli Modena 38kW £815 34kW 16 5 5 7.0kW

 

35-40kW boilers / 14.3 - 16.4 litres per minute

Manufacturer/Model Code Price Heating output (Size) Litres per minute for hot water Standard warranty Free Extended Warranty Min Heating Output
Baxi Platinum 40 £1,260 40kW 16.4 10 10 12.1kW
Worcester Greenstar 8000 35 £1,405 35kW 14.3 5 10 3.5kW
worcester Greenstar 8000 40 £1,600 35kW 16.4 5 10 3.5kW

 

2) Sizing a heat only boiler

It is possible to get a rough idea of the size you need using the age of your property, insulation levels and the size of your property. Property ages are given across the top and they assume standard insulation measures, such as double glazing and loft insulation, have been made. If your levels of insulation are uncharacteristically high for the age of the property then you may wish to move a column to the right. You will note that for the majority of domestic properties, a 6-8kW boiler will be sufficient.

Whilst we show boilers from ranges above this size, in reality they are oversized for domestic properties. There are exceptions of course and the attending engineer should carry out a heat loss survey to accurately size your heat requirement at peak times.

Sizing for your hot water cylinder

One caveat is the output you need for your hot water cylinder, which is often above 8kW. Therefore consider your hot water requirements. Small cylinders commonly need 12kW of heat whilst larger cylinders can take 25kW and upwards. If you have multiple bathrooms in use that the same time then you will need a larger boiler on a conventional setup. The best advice is to pick a boiler than can go down really low on the heating side to get the best efficiencies. See our Guide to the Best Boilers for the most efficient boilers for every situation.

Heat Only Boilers

Age of property pre 1900 1920s-1930s 1950-1980s 1990s 2000 onwards
Insulation levels Poorly insulated Some insulation Moderately insulated Reasonably insulated Well insulated
Number of bedrooms          
1 7kW 7kW 6kW 6kW 4kW
2 8kW 8kW 7kW 6kW 5kW
3 9kW 9kW 8kW 7kW 6kW
4 10kW 10kW 9kW 8kW 7kW
5 14kW 12kW 10kW 10kW 9kW
5+ 16kW 15kW 14kW 12kW 10kW

 

Heat only boilers according to brand and budget:

Use the tables below to find a suitable model. The tables are ordered according to size and closely sized boilers are grouped together in a size bracket, for example 18-21kW. If the sizing table indicates an 18kW boiler for example, then all the boilers in the size group of 18-21kW are applicable.

 

12-13kW boilers

12-13kW Code Price Max Heating Output Standard warranty Free extended warranty Min Heating Output
Potterton Titanium Heat 12 £768.00 13kW 2 2 4.3kW
Ideal Logic Heat 12 £695.00 12kW 2 2 5.1kW
Vaillant EcoFIT Pure Regular 412 £740.00 12kW 2 7 4.5kW
Glow Worm Energy Regular 12 £740.00 12kW 2 2 4.5kW
Vaillant EcoTEC Plus Regular 412 £805.00 12kW 5 10 4.5kW
Ideal Logic + Heat 12 £705.00 12kW 7 7 5.1kW
Worcester Bosch Greenstar Ri 12 £810.00 12kW 5 10 3.5kW
Baxi 200 Heat 12 £600.00 13kW 3 3 7.5kW
Baxi 400 Heat 12 £65.00 13kW 5 5 7.5kW
Viessmans Vitodens 100-W Regular 13 £850.00 13kW 5 10 7.2kW

 

15-16kW boilers

15-16kW Code Price Max Heating Output Standard warranty Free extended warranty Min Heating Output
Main Eco Compact 15 £685.00 15kW 5 5 5.4kW
Glow Worm Energy Regular 15 £755.00 15kW 7 7 4.5kW
Ideal Logic Heat 15 £720.00 15kW 2 2 5.1kW
Vaillant EcoFIT Pure Regular 415 £775.00 15kW 2 7 4.5kW
Potterton Titanium Heat 15 £810.00 15kW 7 7 5.4kW
Ideal Logic + Heat 15 £740.00 15kW 7 7 5.1kW
Worcester Bosch Greenstar Ri 15 £830.00 15kW 5 10 4.6kW
Vaillant EcoTEC Plus Regular 15 £880.00 15kW 5 10 4.5kW
Baxi 200 Heat 15 £630.00 16kW 3 3 7.5kW
Baxi 400 Heat 15 £685.00 16kW 5 5 7.5kW
Viessmans Vitodens 100-W Regular 16 £885.00 16kW 5 10 7.2kW
             

 

18-21kW boilers

18-21kW Code Price Max Heating Output Standard warranty Free extended warranty Min Heating Output
Main Eco Compact 18 £720.00 18kW 5 5 6.4kW
Glow Worm Energy Regular 18 £790.00 18kW 7 7 5kW
Ideal Logic Heat 18 £770.00 18kW 2 2 5.1kW
Potterton Titanium Heat 18 £850.00 18kW 7 7 6.4kW
Vaillant EcoFIT Pure Regular 18 £845.00 18kW 2 7 5kW
Worcester Bosch Greenstar Ri 18 £859.00 18kW 7 8 91%
Vaillant EcoTEC Plus Regular 18 £885.00 18kW 5 10 5.5kW
Baxi 200 Heat 18 £690.00 19kW 3 3 7.5kW
Baxi 400 Heat 18 £715.00 19kW 5 5 7.5kW
Viessmans Vitodens 100-W Regular 19 £900.00 19kW 5 10 7.2kW
Baxi 200 Heat 24 £755.00 21kW 3 3 7.5kW
Baxi 400 Heat 24 780.00 21kW 5 5 7.5kW
Intergas HRE 18OV £759.00 18kW 10 10 6.1kW

 

22-24kW boilers

22-24kW Code Price Max Heating Output Standard warranty Free extended warranty Min Heating Output
Potterton Titanium Heat 24 £888.00 22kW 7 7 8.4kW
Main Eco Compact 24 £755.00 24kW 5 5 8.4kW
Ideal Logic Heat 24 £805.00 24kW 2 2 5.1kW
Ideal Logic + Heat 24 £880.00 24kW 7 7 5.1kW
Worcester Bosch Greenstar Ri 24 £940.00 24kW 5 10 7.3kW
Vaillant EcoTEC Plus Regular 24 £1,035.00 24kW 5 10 6.1kW
Intergas HRE 24OV £829.00 23kW 10 10 7.7kW

 

25-27kW boilers

25-27kW Code Price Max Heating Output Standard warranty Free extended warranty Min Heating Output
Baxi 200 Heat 30 £810.00 25kW 3 3 7.5kW
Baxi 400 Heat 30 £920.00 25kW 5 5 7.5kW
Glow Worm Energy Regular 25 £825.00 25kW 7 7 8.4kW
Vaillant EcoFIT Pure Regular 25 £935.00 26kW 2 7 6.1kW
Viessmans Vitodens 100-W Regular 26 £960.00 26kW 5 10 7.2kW
Intergas HRE 27OV £899.00 27kW 10 10 7.6kW

 

30kW boilers

30kW Code Price Max Heating Output Standard warranty Free extended warranty Min Heating Output
Glow Worm Energy Regular 30 £855.00 30kW 7 7 7.5kW
Baxi 400 Heat 30 £850.00 30kW 5 5 7.5kW
Ideal Logic Heat 30 £910.00 30kW 2 2 6.4kW
Vaillant EcoFIT Pure Regular 30 £987.00 30kW 2 7 7.5kW
Ideal Logic + Heat 30 £922.00 30kW 7 7 6.4kW
Vaillant EcoTEC Plus Regular 30 £1,000.00 30kW 5 10 7.5kW
Worcester Bosch Greenstar Ri 30 £1,065.00 30kW 5 10 7.0kW
Worcester Bosch Greenstar 8000 30 £1,275 30kW 5 10 3.0kW

 

35kW - 41kW boilers

35kW- 41kW Code Price Max Heating Output Standard warranty Free extended warranty Min Heating Output
Viessmans Vitodens 100-W Regular 35 £1,290.00 35kW 5 10 7.9kW
Vaillant EcoFIT Pure Regular 35 £1,458.00 35kW 2 7 7.5kW
Vaillant EcoTEC Plus Regular 35 £1,540.00 35kW 5 10 7.5kw
Worcester Bosch Greenstar 8000 35 £1,510.00 35kW 5 10 3.5kW

 

3) Sizing a system boiler

If your house has seen standard levels of insulation improvements, such as loft insulation or double glazing, then go with the applicable age bracket. If the insulation levels are particularly high relative to its age then move one column to the right. Like heat-only boilers, it is not necessary to install a boiler with a capacity greater than 18kW for the majority of properties, but you must factor in the hot water requirements of your cylinder. Whilst your property might only need 6-8kW of heating, it may still require a bigger output for hot water. There are exceptions and the attending engineer should carry out a heat loss survey to determine the exact figures.

Sizing for your hot water cylinder

A 30-40kW heat only boiler could heat a mansion house, however larger homes with multiple bathrooms in use simultaneously will require a larger output boiler. Some hot water cylinders are set up to take big outputs from the boiler - your heating engineer will be able to assist with the sizing. The best set up is a boiler that can meet your heating and hot water demands and go down really low on the heating side. See our Guide to the best boilers to find the most efficient boilers for every situation.

System Boilers

Age of property pre 1900 1920s-1930s 1950-1980s 1990s 2000 onwards
Insulation levels Poorly insulated Some insulation Moderately insulated Reasonably insulated Well insulated
Number of bedrooms          
1 7kW 7kW 6kW 6kW 4kW
2 8kW 8kW 7kW 6kW 5kW
3 9kW 9kW 8kW 7kW 6kW
4 10kW 10kW 8kW 8kW 7kW
5 14kW 12kW 10kW 10kW 9kW
5+ 16kW 15kW 14kW 12kW 10kW

System boilers according to brand and budget:

Now use the tables below to find the best boiler based on your required size. The tables are in size order and closely sized boilers are grouped together, for example 24-26kW. If the sizing table recommends a 24kW boiler for example, then all the boilers in the size group of 24-26kW are applicable.

 

12-13kW boilers

12-13kW Code Price Max Heating Output Standard warranty Free extended warranty Min Heating Output
Glow Worm Energy System 12 £690 12kW 2 2 4.5kW
Vaillant EcoTEC Plus system 12 £910 12kW 5 10 3.3kW
Vaillant EcoFIT Pure System 12 £865 12kW 2 7 4.7kW
Worcester Bosch Greenstar System i 12 £900 12kW 5 10 3.1kW
             

 

15-17kW boilers

15-17kW Code Price Max Heating Output Standard warranty Free extended warranty Min Heating Output
Glow Worm Energy System 15 £715.00 15kW 7 7 4.5kW
Ideal Logic System 15 £765.00 15kW 2 2 5.1kW
Ideal Logic + System 15 £795.00 15kW 7 7 5.1kW
Vaillant EcoTEC Plus System 615 £960.00 15kW 5 10 3.3kW
Vaillant EcoFIT Pure System 615 £925.00 15kW 2 7 4.7kW
Worcester Bosch Greenstar System i 15 £950.00 15kW 5 10 4.6kw
Ideal Vogue System 15 £905.00 15kW 10 12 3.2kW
Ferroli Modena HE 18S 18 £600.00 17kW 5 5 4.3kW

 

18-21kW boilers

18-21kW Code Price Max Heating Output Standard warranty Free extended warranty Min Heating Output
Potterton Gold System 18 £590.00 18kW 2 2 4.2kW
Glow Worm Energy System 18 £795.00 18kW 7 7 5.0kW
Ideal Logic System 18 £805.00 18kW 2 2 5.1kW
Ideal Logic + System 18 £895.00 18kW 7 7 5.1kW
Vaillant EcoFIT Pure System 18 £1,000.00 18kW 2 7 5.1kW
Vaillant EcoTEC Plus System 18 £1,080.00 18kW 5 10 4.1kW
Worcester Bosch Greenstar System i 18i £1,050.00 18kW 5 10 4.6kW
Ideal Vogue System 18 £985.00 18kW 10 10 3.9kw
Viessmann 100-W System 19 £1,035.00 19kW 5 10 4.3kW
Viessmann 200-W System 19 £1,310.00 19kW 3 10 1.9kW
Baxi 618 System 18 £930.00 19kW 7 7 4.9kW
Intergas HRE 18 £789 18kW 7 7 5.6kW

 

24-25kW boilers

24-25kW Code Price Max Heating Output Standard warranty Free extended warranty Min Heating Output
Potterton Gold System 24 £617.00 24kW 2 2 6.8kW
Ideal Logic System 24 £850.00 24kW 2 2 5.1kW
Ideal Logic + System 24 £860.00 24kW 7 7 5.1kW
Worcester Bosch Greenstar System i 24i £1,060.00 24kW 5 10 7.2kW
Vaillant ecoTEC plus system 624 £1,225.00 24kW 5 10 5.7kW
Ferroli Modena HE 25S 25 £605.00 25kW 5 5 6.2kW
Glow Worm Energy System 25 £845.00 25kW 7 7 6.1kw
Vaillant ecoFIT pure system 625 £1,150.00 25kW 2 7 6.4kW
Main System Eco Elite 24 £617.00 26kW 3 3 8.3kW
Viessmann 100-W System 26 £1,095.00 26kW 5 10 4.3kW
Ideal Vogue System 26 £1,110.00 26kW 10 10 5.6kW
Viessmann 200-W System 26 £1,465.00 26kW 3 10 1.9kW
Ravenheat HE System 98S £649.00 25kW 5 5 3.7kW
Intergas HRE 24 £689.00 23kW 7 7 7.2kW

 

26-29kW boilers

26-29kW Code Price Max Heating Output Standard warranty Free extended warranty Min Heating Output
Worcester Bosch Greenstar System i 27i £1,070.00 27kW 5 10 7.0kw
Baxi System 624 £1,015.00 27kW 7 7 4.9kW
Vaillant ecoTEC exclusive 27 £1,345.00 27kW 5 10 4.2kW
Potterton Gold System 24 £615.00 28kW 2 2 6.8kW
Ravenheat CS System 24 £546 26kW 2 2 4.0kW
Intergas HRE 30 £949.00 27kW 7 7 7.6kW

 

30-32kW boilers

30-32kW Code Price Max Heating Output Standard warranty Free extended warranty Min Heating Output
Glow Worm Energy System 30 £833.00 30kW 7 7 7.5kW
Ideal Logic System 30 £883.00 30kW 2 2 6.4kW
Ideal Logic + System 30 £902.00 30kW 7 7 6.4kW
Viessmann 100-W System 30 £1,070.00 30kW 5 10 9.1kW
Worcester Bosch Greenstar System i 30i £1,105.00 30kW 5 10 7.0kW
Vaillant EcoTEC Plus System 30 £1,308.00 30kW 5 10 6.4kW
Vaillant EcoFIT Pure System 30 £1,212.00 30kW 2 7 7.5kW
Viessmann 200-W System 30 £1,545.00 30kW 3 10 1.9kW
Ideal Vogue System 32 £1,187.00 32kW 8 10 6.8kW
Worcester Bosch Greenstar 8000 30 £1,310 30kW 5 10 3.0kW
             

 

34-37kW boilers

34-37kW Code Price Max Heating Output Standard warranty Free extended warranty Min Heating Outpu
Potterton Promax System 32 £948.00 34kW 2 2 94.kW
Viessmann 100-W System 35 £1,511.00 35kW 5 5 5.4kW
Viessmann 200-W System 35 £1,571.00 35kW 3 10 1.9kW
Vaillant EcoTEC plus system 37 £1,312.00 37kW 5 10 7.1kW
Worcester Bosch Greenstar 8000 35 £1,352.00 35kW 5 10 3.5kW

Achieving even better efficiencies with compatible thermostats

Sizing the boiler correctly is the first step to an efficient heating system. The next step is to pair the boiler with an advanced heating control that can adjust the output to suit the outside temperature. These are forms of ‘modulating’ control which will reduce the output of the boiler from its maximum, say 10kW, down to 2kW during spring and summer. This means that the boiler will run efficiently at the right output required by your home all year round. For more on advance controls try our Guide to Advanced Heating Controls.

Jo Alsop

Heating Hero

The Heating Hub

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