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Boiler Repair or Boiler Replacement?


Jo Alsop

Heating Hero

The Heating Hub

Boilers should last 22 years. If you have been advised to replace too early you need to question the advice.


When are the circumstances right to repair your boiler? When should you consider boiler replacement?

We have one of the highest replacement boiler rates in Europe and we frequently swap working boilers out at early as 5-7 years when they should last 22 years. It is a problem unique to the UK a results from either bad advice or bad installations. In most cases your money would be better invested making your existing boiler and heating system more efficient. We guide you on what to do if your boiler needs repair and seriously consider if it actually needs replacement.

Consider the reasons for replacement


Very old boilers have very few parts to go wrong and in some ways this makes them reliable and often easy to repair. However they are likely to be around 60% efficient, by which we mean 40% of the heat produced goes straight out of the flue. A decision to replace may not be based on reliability, rather on efficiency.

Some boilers, even those manufactured in the last 10 years, have proved themselves to be enormously unreliable through poor design. In fact many boiler cover policies exclude them explicitly. Most take the decision to cut their losses and replace rather than continue with expensive and unreliable repairs.

Most boilers will start to need some new parts at 10-15 years but this is not a reason to replace the boiler. Investment in the boiler in later years is standard, just as it is with a car.

Parts availability

Many of us have at one time received advice to replace, often from our boiler cover providers, on the basis that many parts are ‘unavailable’ or ‘obsolete.’ This advice may be imparted by an engineer during a call out to your boiler or in writing from your boiler cover provider.

Be warned, a letter that advises that “some parts are no longer available” may not necessarily signify the death knell for your boiler! Manufacturers discontinue non-essential parts such as body casing quite early on but continue to manufacturer replacement mechanical and electrical components such as gas valves, fans, printed circuit boards (PCBs), diverter valves and heat exchangers for some time. Ring the boiler manufacturer’s technical helpline to find out what is being discontinued.

Home improvements

A natural point to upgrade your old boiler is when you have to change the location or boiler type due to a new kitchen, a new extension or adding bathrooms. You may wish to limp along with your old boiler until then!

Where parts are genuinely obsolete, a boiler cover provider may no longer attend call outs to that fault. However many will fit customer sourced parts which can be found on ebay and other second-hand sites. Repair or replace really depends on how long you wish to hang on to your old boiler and risk breakdown with a diminishing chance of repair.

A standard assessment is that adding bathrooms and floor area will need a bigger boiler. This is rarely the case as boilers are massively oversized in all UK homes. Better to assess the capabilities of the existing boiler and invest in its efficiency.


Efficiency is not always a reason in itself to replace an old boiler, but in some cases where the boiler is only 60-70% efficiency it is a very good one (work out your boiler's efficiency with our Guide to Boiler Efficiency)

You need to consider three things:

  1. Whilst modern condensing boilers show 'factory-tested' efficiencies of 89% or more, few achieve this for any significant period of time due to systematic oversizing of boilers (the average UK home needs just 6-8kW of heat at peak times but we regularly fit 18-24kW boilers) and no requirement to fit controls that decrease the boiler's output during off-peak periods (known as modulating controls). For more see our comprehensive guide: Why condensing boilers do not contense.
  2. How long will it take to recoup the cost of a new boiler? If you save £200 per year in energy bills and have no repairing liability under the new boiler warranty, then you may recoup the cost in a matter of years. however, the boiler must be sized correctly and paired with a compatible modulation control - for more see our Guide to Opentherm and other modulation controls
  3. For those with green credentials, just consider this: retaining a working, albeit slightly inefficient boiler (compared to modern standards) will likely have a lower environmental impact than the environmental cost of manufacturing a new model, particularly in light of points 1 and 2.


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Help ‘hanging on’ to your old boiler

You may have very good reasons to keep your old boiler working for just a little longer..

  • You are undertaking home improvements in the next 12 months which include moving the boiler or upgrading to a new boiler anyway
  • You cannot afford a new boiler this year
  • You are moving house and do not want the expense of a new boiler

Options for keeping it going:

  • Take out boiler cover for a monthly sum, it’ll cost around £200 per annum (depending on the type of cover) and its cheaper than a boiler replacement. NB make sure your boiler is covered – some older/poorly designed models are excluded from boiler cover policies – read ourGuide to Boiler Cover Plans for more.
  • Research the main components of the boiler that are likely to go or have ‘gone’. E.g. gas valves, fans, printed circuit boards (PCBs) diverter valves and heat exchangers. All parts have a manufacturer number and what is called a GC number. If the number is not on the part itself you will find it in the manufacturer’s instructions, which you can find on line. If the manufacturer is still around, or has been bought out by another, you will likely be able to find out the boiler model or part number via their technical help line. If the part is no longer available via plumbers merchants such as Plumb Center, or Grahams, source the part via Ebay, which is very good for listing parts via their manufacturer part number or GC number.

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