Should I Repair or Replace My Boiler? A Practical Guide

When a boiler breaks down, the question soon follows: is it worth fixing, or is it time for a new one? There is no single answer, but the decision usually comes down to a handful of things you can weigh up with the right information. This guide sets them out, along with a simple rule of thumb and the questions worth asking an engineer.

A simple rule of thumb

If a repair costs more than about a third of the price of a replacement, and the boiler is more than 10 to 12 years old, replacement usually wins. Below that, a repair is often the better value, especially on a younger boiler with a good service history.

It is a starting point rather than a rule. The sections below cover the things that can tip the decision either way.

The things that decide it

How old the boiler is

A well-maintained gas boiler commonly lasts around 10 to 15 years. A boiler in its first few years is almost always worth repairing. As it gets older, each repair buys less time, because other parts are wearing out too.

What has failed

Some faults are small and self-contained: a pump, a diverter valve, a fan, a sensor or an expansion vessel. Replacing one of those can give a boiler years more life. Others are major: a failed heat exchanger, for example, is one of the most expensive repairs and on an older boiler often costs a large share of a new one.

Whether parts are still available

Manufacturers stop making parts for older models over time. When parts become hard to find, repairs take longer and cost more, and the next breakdown may not be repairable at all.

Warranty

If the boiler is still under its manufacturer's warranty, a repair may be covered. Most warranties need an annual service by a Gas Safe registered engineer to stay valid, so keep the service records.

How often it breaks down

One repair in several years is normal wear. Repeated breakdowns, especially different faults one after another, are a sign that the boiler as a whole is nearing the end of its life.

Efficiency and running costs

Condensing boilers became the standard for new gas boiler installations in England and Wales in 2005. A boiler fitted before then may well be a non-condensing model that wastes more of the gas it burns. Replacing one of those can make a noticeable difference to running costs; replacing a ten-year-old condensing boiler with a new one usually makes less.

Safety

If an engineer finds that a boiler is unsafe, it is turned off or disconnected under the Gas Safe Register's unsafe situations procedure, and it must not be used until it has been put right. Whether that means a repair or a replacement depends on what is wrong, and the engineer should explain the options and their costs.

When repairing usually makes sense

• The boiler is under 10 years old
• It is still under the manufacturer's warranty
• The fault is a single part that is still available
• It has a good service history and rarely breaks down
• The repair is small compared with the cost of a new boiler

When replacing usually makes sense

• The boiler is well over 10 to 12 years old
• The repair would cost a large share of a new boiler
• It keeps breaking down with different faults
• Parts are obsolete or hard to get
• It is an old non-condensing model and running costs are high
• Your hot water needs have changed, for example after adding a bathroom

Questions to ask the engineer

1. What exactly has failed, and what does the repair cost, including parts?
2. How old is the boiler, and are parts still available for it?
3. Is anything else on the boiler showing signs of wear?
4. Is it still under the manufacturer's warranty?
5. If I replaced it, what type and size of boiler would suit my home, and what would it cost?

A good engineer will answer all five plainly and tell you when a repair no longer makes financial sense, rather than pushing either option.

If you decide to replace it

A new boiler starts with a survey: the size of your home, how many bathrooms are in use, your water pressure, where the flue can go and the condition of the existing system. That decides whether a combi, system or conventional boiler suits you best, which is explained in the guide to combi, system and conventional boilers.

Getting an honest answer in South London

InstaGasWorks repairs and replaces boilers across South West London, Croydon and Sutton. A breakdown visit finds the fault and prices the repair before any work starts, so you can make the decision with the figures in front of you. If replacement makes more sense, the boiler installation page explains what a new boiler includes and how the free survey and written quote work.