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Heat only boiler guide 2021 | We compare prices on 67 boiler models

07/06/2020

Jo Alsop

Heating Hero

The Heating Hub

Heat-only boilers are only used to replace existing heat-only boilers. They can have limited efficiency potential.

 

What is a heat only boiler? Who offers the best heat only boiler prices in 2020?

A heat-only boiler, aka a conventional or regular boiler, works with a hot water cylinder in the airing cupboard on an open vented (tanks in the loft) or sealed heating system. Heat only boilers can be a cost effective replacement, from £480 for a small, entry-level boiler to £1,600 for a premium model. In this guide, we compare the prices, sizes, efficiencies and warranty lengths of 67 models from 11 of the leading boiler manufacturers in the UK, including Worcester Bosch, Baxi, Ideal and Vaillant. The best heat only boiler for you will be based on your property size and your budget. 

Find your best heat only boiler

The tables are arranged so that you can easily find your property size and then find who offers the best boiler package for your budget. The tables show boiler price alongside warranty period and efficiency so you can find the best value boiler. Most boiler manufacturers produce one or two models of regular boiler with outputs between 12kW and 40KW and everything inbetween. Unlike combi and system boilers, there is not such a great disparity between prices at the lower and upper ends. That is not to say that they are all the same, we have still found great value boilers in all categories.

Sizing your heat only boiler

Modern boilers are almost universally oversized. The average UK home requires just 6-8kW of heat at peak times. The most popular heat only boiler is around 15kW, more than twice the capacity most homes will ever need. So what is wrong with oversizing, just in case?

Firstly the boiler will cycle on and off more than it was ever designed to, accelerating wear and tear.
Secondly it will rarely operate at its most efficient, i.e. in 'condensing mode', because the return temperatures to the boiler will be too hot. Condensing boilers need the temperature of the water as it flows back to the boiler to be 50 degrees C or less. This requires a correctly sized boiler AND a perfectly balanced system with TRVs that signal the boiler to reduce its output further (modulate) as each room gets warm enough.


The good news is that most modern boilers can be 'ranged rated' down, i.e. the output reduced to more closely match your property's heat requirement, which is calculated by the attending engineer. Make sure you check that the engineer has done this. For more see our Guide to Boiler Sizing.

In some cases you will require a larger boiler however based on the capacity of your hot water cylinder coil. Coils (like an element in a kettle) may need 12kW or 25kW, depending on their size. The attending engineer will be able to assist with sizing for your hot water requirements.

Search our boiler tables

As outlined above, the average UK home needs 6-8kW of heat at peak times. As is evident below, it is not currently possible to buy a 6-8kW boiler, the smallest heat only boiler available is 12kW and anyway you will likely need at least 12kW for a small hot water cylinder. The good news is that you can range rate it down (see boiler sizing section above). In terms of product, the Vaillant offers the best all-round value as it goes down pretty low and comes with a 7 year warranty.

1-3 bed house with small hot water cylinder

Boiler Model Price Standard warranty Free extended warranty Maximum heating output Minimum heating output
Baxi 200 Heat 12 £600 3 3 13 7.5
Baxi 400 Heat 12 £654 5 5 13 7.5
Ideal Logic Heat 12 £695 2 2 12 5.1
Ideal Logic + Heat 12 £705 7 7 12 5.1
Potterton Titanium Heat 12 £768 7 2 13 4.3
Vaillant ecoFIT pure regular 412 £740 2 7 12 4.5
Glow Worm Energy Regular 12 £740 7 7 12 4.5
Vaillant ecoTEC plus regular 412 £805 5 10 12 4.5
Worcester Bosch Greenstar Ri 12 £810 5 10 12 3.4
Viessmans Vitodens 100-W Regular 13 £850 5 10 13 7.2
Viessmans Vitodens 100-W Regular 19 £900 5 10 19 7.2
Worcester Bosch Greenstar 8000 30 30 £1,275 5 10 30 3

 

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1-3 bed properties with large hot water cylinder

    Price Standard warranty Free extended warranty Maximum heating output Minimum heating output
Baxi 200 Heat 15 £630 3 3 16 7.5
Baxi 400 Heat 15 £685 5 5 16 7.5
Main Eco Compact 15 £685 5 5 16 5.4
Ideal Logic Heat 15 £720 2 2 15 5.1
Ideal Logic + Heat 15 £740 7 7 15 5.1
Glow Worm Energy Regular 15 £755 7 7 15 4.5
Vaillant ecoFIT pure regular 415 £775 2 7 15 4.5
Potterton Titanium Heat 15 £810 7 7 16 5.4
Worcester Bosch Greenstar Ri 15 £830 5 10 15 4.6
Viessmans Vitodens 100-W Regular 16 £855 5 10 16 7.2
Vaillant ecoTEC plus regular 415 £880 5 10 15 4.5
Viessmans Vitodens 100-W Regular 19 £900 5 10 19 7.2
Worcester Bosch Greenstar 8000 30 30 £1,275 5 10 30 3

4 bed house

    Price Standard warranty Free extended warranty Maximum heating output Minimum heating output
Baxi 200 Heat 18 £690 3 3 19 7.5
Baxi 400 Heat 18 £715 5 5 19 7.5
Main Eco Compact 18 £720 5 5 19 6.4
Intergas HRE 18 18 £759 10 10 18 6.1
Ideal Logic Heat 18 £770 2 2 18 5.1
Ideal Logic+ Heat 18 £780 7 7 18 5.1
Glow Worm Energy Regular 18 £790 7 7 18 5.0
Vaillant ecoFIT pure regular 418 £845 2 7 19 5.0
Potterton Titanium Heat 18 £850 7 7 19 6.4
Worcester Bosch Greenstar Ri 18 £885 5 10 18 5.5
Viessmans Vitodens 100-W Regular 19 £900 5 10 19 7.2
Vaillant ecoTEC plus regular 418 £965 5 10 19 5.0
Worcester Bosch Greenstar 8000 30 30 £1,275 5 10 30 3

5 bed house

You are unlikely to need a 25kW boiler for your heating, but if you have a 25kW hot water cylinder coil then you will need a larger heat only boiler.

  Price Standard warranty Free extended warranty Maximum heating output Minimum heating output
Main Eco Compact 24 24 £755 5 5 25 8.4
Baxi 200 Heat 24 £755 3 3 21 7.5
Baxi 400 Heat 24 £780 5 5 21 7.5
Ideal Logic Heat 24 £805 2 2 24 5.1
Glow Worm Energy Regular 25 £825 7 7 25 8.4
Intergas HRE 24 24 £829 10 10 23 7.7
Ideal Logic + Heat 24 £880 7 7 24 5.1
Potterton Titanium Heat 24 £888 7 7 25 8.4
Intergas HRE 27 27 £899 10 10 27 7.6
Vaillant ecoFIT pure regular 425 £935 2 7 26 6.1
Worcester Bosch Greenstar Ri 24 £940 5 10 24 7.3
Viessmans Vitodens 100-W Regular 26 £960 5 10 26 7.2
Vaillant ecoTEC plus regular 424 £1,035 5 10 24 6.1
Worcester Bosch Greenstar 8000 30 30 £1,275 5 10 30 3

 

Heat only boiler basics

A heat only boiler (also known as a regular boiler or conventional boiler) provides heat directly to the radiators and works with a vented hot water tank to provide hot water. Heat only boilers can work on 'open vented' or 'sealed systems' (to work out which system you have and the advantages and disadvantages of each read our Guide to Open Vented and Sealed Systems). Replacing a heat only boiler is very cost effective, however long term maintenance costs will be higher as many of the systems components (pumps, valves etc) are external to the boiler. They also have limited efficiency potential as they rarely work with modern modulation controls.

When is a heat only boiler right for my home?

Heat only (regular) boilers are are usually only a replacement for an existing heat only boiler. This is because it is more cost effective in terms of long term maintenance to install a combi or system boiler as more the system's components are integral to the boiler (pump, valves etc) and therefore covered by the manufacturer's warranty.

If you are replacing your heat only boiler and considering other boiler types, the main two things to remember are 1) a heat only boiler can work on an 'open vented' system (you will have water tanks in the loft). If you wish to retain your open vented system then you will have to go with one of the heat only boilers that can work in this system configuration (see also our Guide to Open Vented and Sealed Systems). 2) If you have poor incoming water pressure then a combi or system boiler may not work. 

 

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