James Elston

James Elston

Published March 9, 2024

On average, boilers need to be replaced every 10 to 15 years. If a boiler is made of cast iron, then it might not need to be replaced for 20 to 30 years. However, this can vary widely depending on the model, the hot water demands of your home, and how well the boiler is maintained.

Eco Happy will guide you through the telltale signs that indicate your boiler needs replacing. We’ll also tell you what you need to consider when buying a new one, and give you some tips on how to increase the lifespan of your existing boiler.

7 Signs Your Boiler Needs Replacing

Here are the seven most common signs that your boiler needs to be replaced.

1. It’s very old

As mentioned, a boiler should last for around 10 to 15 years. Regular servicing and maintenance can extend its lifespan but, generally, if it’s over 15 years old, it probably needs to be replaced.

The main reasons for this are a lack of efficiency compared to new boilers, the increased likelihood of major issues and full breakdowns, and the difficulty in sourcing replacement parts when they inevitably do need fixing.

As a boiler ages, the parts required to repair it become harder to find as they gradually stop being produced. Even if parts can be sourced, their scarcity means they tend to be very expensive and it becomes more cost-effective to buy a new boiler rather than repair the old one.

2. It breaks down regularly

If you’re having to call out an engineer several times a year to resolve issues with your boiler, it’s definitely time to consider a boiler replacement.

On average, it costs between £100 and £500 to have a boiler repaired. So, if you have to pay this multiple times a year, it can quickly become very pricey and it would cost less money in the long term to get your current boiler replaced with a new one.

Of course, if your boiler needs a few repairs in a short space of time but then starts running well without any issues, then it might not need replacing just yet.

If you’re unsure, ask an engineer for their opinion when they come to repair your boiler. They’ll be able to tell you whether it’s worth persisting with your boiler or whether it’s time for a new one.

3. It’s very noisy

If you notice that your boiler or central heating system is making noises, it’s usually nothing to worry about. When water circulates through the system and pipes contract and expand, a certain amount of noise is normal.

However, unusual boiler noises like banging, whistling, rattling, and gurgling can often be signs of a fairly serious issue.

For example, banging noises can be a sign of “kettling,” which is often caused by limescale buildup in the boiler or central heating system. It could also be caused by a faulty boiler pump.

With a new boiler, it would make sense to simply have the pump replaced. Yet, as we mentioned earlier, replacement parts for old boilers are few and far between, and expensive – if you can find them at all. So, it might make more sense to get a replacement boiler instead.

4. Consistent low water pressure

Over time, you might have noticed that the water pressure in your home has decreased steadily. This could be because of a faulty pressure relief valve. In this case, you can find out how much it would cost to replace it and see if it makes sense to do this.

However, the most likely cause is that the boiler’s pipework has loosened and corroded over the years. If you’ve noticed a fair few leaks lately, this is probably why.

Again, it’s a case of weighing up the costs of having your existing boiler repaired or paying for a new unit. Most of the time, it makes financial sense to replace your boiler.

5. Unusual odours

If you smell a sulphurous, eggy odour coming from your boiler, this means there’s a gas leak. In this scenario, you need to turn your boiler off, open all the windows and doors in your home, and evacuate immediately.

You should then call the National Gas Emergency line on 0800 111 999.

Once the leak has been dealt with, an engineer will be able to tell you what’s caused it. The most likely culprits are:

  • A corroded heat exchanger
  • Faulty joints or seals
  • A leaky auto-air vent
  • A damaged blowdown valve
  • Poor installation or maintenance

If the cause is faulty joints or seals, it might not be too expensive to fix. On the other hand, if any of the vital components of the boiler need to be replaced, then it’s probably time for a new boiler.

A serious issue with your boiler could also lead to a carbon monoxide leak. In this case, there wouldn’t be a smell, as carbon monoxide is both odourless and invisible.

The signs of a carbon monoxide leak include:

  • Soot deposits on or around the boiler
  • A yellow boiler flame instead of a blue one
  • The pilot light keeps going out
  • People in your home are experiencing headaches, nausea, and dizziness

If you suspect there’s a leak, follow the steps we laid out above for a gas leak.

6. Your energy bills keep going up

Granted, energy bills are high for everyone at the moment, but if you have a particularly old boiler, yours might be even higher than you’d expect.

This is likely due to the fact that older boilers are far less energy efficient than new boilers. For instance, a modern combi boiler may have an energy efficiency rating as high as 98% and most modern combi boilers are Energy-related Product (ErP) A-rated. This means that only around 2% of the energy it uses is wasted.

On the other hand, many older boilers are now G-rated, meaning they waste a significant amount of energy whenever they’re running. As a result, you’ll be paying much more for your energy bills than you should be.

Installing a more efficient boiler will likely reduce your bills and save you money in the long run – even if it’s a big initial investment.

7. It’s no longer able to meet your hot water demands

When you first had your boiler installed, it may have been perfectly suitable for your home’s hot water demands. Yet, since then, your family might’ve grown, or perhaps you’ve added a new bathroom or two.

If so, your old boiler may not have enough power to satisfy the hot water requirements of your home anymore, and it’s time to have it replaced.

How Much Does It Cost To Replace Your Boiler?

So you’ve decided that you need to buy a new boiler, but how much is this going to cost you? On average it costs between £1,500 and £4,500 to buy a new boiler and have it installed.

A new boiler costs between £500 and £3,000 on average, while the installation cost is usually between £650 and £2,500.

The price can vary widely depending on the type of boiler, the size of your property, and the number of engineers required, among other factors.

Although boiler replacement costs can be high, you’re almost guaranteed to save money over time due to fewer repairs and improved efficiency.

Factors To Consider When Choosing A Replacement Boiler

These are the most important things to consider when choosing a replacement boiler.

Your budget

Carefully consider the full expenses of a new boiler, including the unit price and the boiler installation costs. Weigh up your options and make sure you compare quotes from different installers and boiler manufacturers.

The size of your home

You need to ensure your new boiler can meet the hot water demands of your home. In other words, the boiler must have the right power output levels.

For example, if you live in a small home or apartment with 10 radiators and one bathroom, a combi boiler with a central heating (CH) output of 24-27 kW should suffice. Combi boilers are also compact and can be wall-mounted, making them ideal for smaller homes.

If you live in a large home with 20 radiators and two bathrooms, a system boiler with a CH output of 32-40 kW would be more suitable.

Energy efficiency

You should make sure you buy an ErP A-rated boiler – it must have at least a 90% efficiency rating to earn this status. This means at least 90% of the energy it uses is converted into usable heat, which reduces your carbon footprint and your energy bills.

The warranty

All the leading brands, including Vaillant, Ideal and Worcester Bosch, offer boilers with 7- to 12-year warranties. You should aim to purchase a boiler with a warranty of this duration (or, at minimum, a 5-year warranty).

You’ll then be covered for any repairs to your boiler for a long time – and you may even be covered for a full replacement in the future.

What Steps Can I Take To Increase My Boiler’s Lifespan?

Although your boiler will need to be replaced at some point, there are a few things you can do to boost its longevity.

Annual service

Most people know it needs to be done at some point, but how often exactly does a boiler need to be serviced? Getting your boiler serviced annually is vital, because it allows an engineer to address minor issues before they develop into more serious ones.

This can reduce the need for major repairs and potentially prolong the life of your boiler.

Regular maintenance

There are also some steps you can take to maintain your boiler and possibly add some years to its life, such as:

  • Insulating pipes to increase heat retention
  • Lagging external pipes to prevent freezing
  • Applying a corrosion inhibitor to the central heating system to prevent sludge buildup
  • Bleeding your radiators to remove trapped air from the system
  • Regularly checking for leaks
  • Flushing the system to clear any blockages (you’ll need an engineer for this)

Smart controls

Certain smart controls (like modulating thermostats) adjust a boiler’s output based on demand. This removes some of the strain on the boiler and helps it operate more efficiently, improving its longevity.

Compare Quotes For Replacing Your Boiler With EcoHappy

Besides the price of the unit, having it installed is the most costly part of replacing a boiler. That’s why you should compare boiler installation quotes with Eco Happy. We take the hassle and stress out of finding the most affordable rates possible.

Provide us with some basic information and we’ll compare quotes from installers in your area within seconds. Getting expert advice is the easiest way to save yourself money when you replace your boiler.


Am I responsible for replacing my boiler if I live in a rented property?

The landlord is generally responsible for replacing the boiler in a rented property. Under the Landlord and Tenant Act 1985, landlords are required to keep boilers in proper working order and good repair. This means they’re also responsible for arranging annual services and any necessary repairs.

If you suspect the boiler in your rented property needs replacing, contact your landlord and they should arrange for it to be repaired or replaced.

Can I pay for a new boiler in instalments?

Yes, many boiler suppliers allow you to spread the costs of a new boiler out over a set period. Usually, this equates to paying the boiler off in monthly instalments.

Some companies offer 0% interest and 0% deposit financing for a certain period, such as two years.

How can I dispose of my old boiler responsibly?

The easiest way to dispose of your old boiler responsibly is to ask the installer to take the unit with them when they leave. Often, they’ll do this for free, although some will ask for an additional payment.

Final Thoughts

Although replacing a boiler is a big investment, you’ll almost certainly make your money back on reduced energy bills and fewer repairs.

Remember: the most important things to consider when choosing a new boiler are your budget, the size of your home, and the length of the warranty. Plus, it’s also crucial to compare installation quotes to make sure you get the best deal.

James Elston

James Elston

Boiler Expert

James Elston is the top boiler replacement and heating expert at Eco Happy. He has over 20 years of experience in the industry, focusing on Gas Safe boiler installations and offering home-heating and energy-saving solutions to homeowners across the UK. From sourcing the most energy-efficient combi boiler to providing specialist heating advice, James ensures that Eco Happy maintains the highest standards and best customer service.

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