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Last updated: 31st July, 2023


How Long Will A Back Boiler Conversion Take?

How Long Will A Back Boiler Conversion Take?

A back boiler conversion could be your ticket from the past to the present, where boilers can be sleek, efficient and best of all… actually save you money!

A back boiler conversion could be your ticket from the past to the present, where boilers can be sleek, efficient and best of all… actually save you money!

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What Is A Back Boiler?

Back boilers are an old, antiquated variety of boiler that can be found fitted behind an open fireplace, instead of in its own designated area i.e a storage cupboard.

A cheaper alternative heating system compared to boilers in the past, most back boilers were replaced or upgraded to newer systems in 2005 due to regulation changes.

Drawbacks Of Back Boilers

Back boilers are not the financially viable option they once were, and with the relentless progression of technology in home heating development, they now present several negatives surrounding their performance.

Poor Efficiency

Back boilers date back decades since their introduction, therefore their efficiency is nowhere near today's high standard of energy to heat conversion.

Back boilers could be up to 70% less efficient than a modern combi boiler, a shocking stat that could be costing you hundreds of pounds per year in wasted energy.

Age of Boiler

Efficiency Percentage

Efficiency Rating (ErP)

0+ Years

90% +


10+ Years

85% +


15+ Years

80% +


20+ Years

70% +


25+ Years

60% +


The direct correlation between a boiler’s age and its efficiency is clear to see in the newer systems’ ErP, so it may be worth upgrading your model to an energy efficient boiler.

Very Difficult To Repair 

Due to the age of back boilers, and the subsequent sparsity in their part availability, they are notoriously difficult to repair, even for a qualified Gas Safe engineer.

Take Up A Lot Of Space

Due to the positional functionality of back boilers, if you aren’t actively using your fire or fireplace, they tend to eat up a lot of space which could be used for other purposes within such a high traffic and primary occupied room.

Noisy and Draughty

Due to their prehistoric ventilation systems, back boilers can often contribute to heat negating draughts and peace disturbing operating noise.

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Back Boiler Conversions

Time Frame

At iHeat we advise that every installation and conversion is a unique undertaking and time frames are intended only as a guide - for a back boiler conversion carried out by a Gas Safe engineer we recommend you should allow for up to two days of work.


Firstly, you need to decide on whether you want the back boiler upgrading to a combi or system boiler, systems can work out cheaper in terms of the conversion due to a lot of the pipework remaining the same.

However, most people opt for the combi conversion as an upgrading of the entire system could be more efficient in the long run, and may ensure less future faults, reducing repair or maintenance costs.

Secondly, you will need to decide upon the new flue placement of a combi for example, you could keep the same vertical flue position, releasing gases out of the chimney or move it due to the fact combis can operate with a vertical or horizontal flue.

Thanks to the compact design of modern combi boilers, they can be positioned into smaller spaces like a standard kitchen cupboard, or they can be placed in the same spot as the boiler being removed (if you want your boiler moved to a new location there will be additional fees, especially if there is no piping in this area).

The fire will need to be removed, followed by the old boiler, flue, tanks and all relevant piping will be re-routed or installed.

Post new boiler installation any area repairs to surrounding walls or where the fire previously was will need carrying out and safety checking.

Back Boiler Conversion Costs

Every back boiler conversion cost, like any heating system installation, varies on job specifics such as installer rates, straight swap or relocation and new heating unit costs, average prices can range from £600-£800 (not including new boiler costs).

Do You Need A Back Boiler Converting To A Modern Boiler?

If you’ve liked what you've been reading and want an old inefficient boiler replaced, or just fancy an upgrade, get a fixed price, free quote on a wide selection of boilers with gas safe registered installation here at iHeat.

Our expert heating engineers can carry out the conversion of an old, energy frivolous, redundant back boiler to a powerful and space saving new heating system with minimum disruption and guaranteed energy savings upon completion.

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Stephen Day profile photo
Article by
Stephen Day | Co-founder
Gas Safe registered and FGAS certified engineer with over 20 years experience in the heating and cooling industry.