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Are New Boilers Really More Efficient

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  • 28-04-2022
Are New Boilers Really More Efficient

Are new boilers really more efficient? We look at how efficient old boilers are and why new boilers are more efficient.

How efficient is my old boiler?

Modern condensing boilers are labelled as somewhere between 92 to 94%. Whereas boilers that are over 25 years old can have an efficiency percentage as low as 60%, this is also known as a G-rating. 

Unfortunately, it is not as simple as just swapping out your old boiler for a new one and reducing your fuel bills by 30%.

Not all condensing boilers have an A level efficiency rating right out of the box. The majority of newly installed boilers will run at about 10 to 25% under their highest possible efficiency. 

This is due to incorrect installations and the installer not having the correct knowledge about setting up condensing boilers.

What is boiler efficiency?

A boiler's efficiency is measured as the percentage of the system's total energy, which is used in order to create heating for your property. For example, many modern heaters have a boiler efficiency of around 94%.

This means that 94% of all energy that is used by the system will be put towards heating your property while the other 6% is either lost or used for running itself. 

So, with older boilers that have efficiencies of around 60%, a huge 40% of the energy you are paying for is lost in the process. Only 60% will actually be used for heating your home.

Just like all other domestic appliances, boilers have efficiency ratings. These ratings range from an A all the way down to G. Modern boilers must be A-rated, and they have to prove this in the literature that comes packaged with the boiler.

With older boilers, it is much more difficult to determine the efficiency rating due to the ratings being applied retrospectively rather than at the time of production. Below is a quick guide to efficiency ratings and the efficiency percentages to go along with them.

  • A - 90% and higher
  • B- 86-90%
  • C - 82-86%
  • D - 78-82%
  • E - 74-78%
  • F - 70-74%
  • G - lower than 70%

Why are new boilers more efficient?

Every modern boiler you will see is what is known as a condensing boiler. These boilers work on a slightly different system to boilers of decades past which allows them to recover heat that was lost through the flue.

This is used to pre-heat the whole heating system. For the more technically minded people out there, this is done through a second heat exchanger.

The issue with condensing boilers is that they are not necessarily A-rated directly out of the box.

The heat which is been lost through the flue is captured by a second heat exchanger, but it can only do this if it has been reverted back into water vapour.

This is where the term condensing comes from. For this to be done, it needs the system to run at a much lower temperature. The lower the temperature, the better and more efficient the whole system will run.

Unfortunately, when being installed straight out of the box, condensing boilers are rarely changed from their default factory settings.

This means that they run at a temperature of around 80 degrees Celcius.

This temperature is not low enough to allow condensing to take place, and a huge chunk of useful heat will be lost through the system's flue.

Are new boilers really more efficient?

How much money can a new boiler really save me?

As energy costs are only getting higher and higher, it is becoming increasingly important to get the most out of your heating system. 

Households across the country are spending 60% of their yearly energy costs simply on heating, and because of this, more people are looking for ways to save on their energy bills. The top way to do this for many people is to take a look at their boiler efficiency.

This is a fantastic way to cut down on your overheads. Huge swaths of people are creating energy savings just through the act of replacing their boilers. 

Though this might appear to be an expensive option that should only be used when your boiler completely stops working and a new one is required, it can actually end up being one of the cheapest options if you are looking at long-term solutions and need to reduce your heating bills. 

Which are the most efficient boilers? 

In our modern times, all boilers must be rated at an A-level, with factory tested efficiency levels of between 92-94% (ErP) or higher. 

Though, this percentage is actually rarely achieved once the boiler is put into practice in someone's home because there are extra variables which can affect the rating. 

You have to remember that the boiler is simply just one part of the heating system and the whole system needs to work together perfectly in order to result in an efficiency percentage of 90% or higher.

The boiler must be chosen correctly, and it is also highly important that the boiler is fitted correctly as well. Even the best boiler on the market is only as good as the installer that has fitted the system. Below is some extra guidance on picking the correct boiler for your home and your system.

Firstly, the boiler needs to have a low minimum output. All boilers operate within a particular range. For example, between 3 to 30kW or between 8 to 24kW. 

The lower the minimum end of the scale, the better efficiently the whole boiler will run all year round. Most boilers you will find recommended online will have a low minimum output, but it is still important to keep an eye out for them.

Secondly, the boiler needs to be the correct size. The majority of homes around the UK only need 6 to 8kW on a particularly cold day. For the rest of the year, you will require even less. The issue is that most boilers are much bigger than this. Due to this, it is important that when your new boiler is installed that your installer reduces the maximum output of the system.

Next, any boiler you decide to purchase must be paired up with compensation controls. Modern boilers have the ability to vary their output both up and done in order to meet the demands of changing temperatures. 

This is highly efficient but only works as it should once it is paired with a control which can communicate with the boiler. Keep this in mind when shopping around for a new system.

Finally, and this one is very important, ensure that your boiler is installed by a fully trained and knowledgeable expert. If your boiler is installed by someone who does not know what they are doing, then the whole system can end up not working as required, leading to your energy bills boosting even further. 

The difficulty is that the majority of installers have not been trained on how they should set up condensing boilers correctly. This is due to many boiler installers having their training before condensing systems were even a factor.

We would recommend asking around before you make a choice on which professional to use. Perhaps even ask if the installer has any history with installing condensing boilers.

Boiler Energy Ratings

The efficiency of a boiler is commonly determined by the type of unit in question, as well as how old the unit is.

Boilers which have been used for a long time are much less efficient than newly installed units. This is due to both the boiler's design and continuous use over a long period of time.

You will find that boiler efficiency is often categorised by a percentage. This is a development and extension from the usual A to a G rating system, which you will see on your other household appliances.

Boilers which are A-rated are more than 90% efficient. This means that only 10% or less of the energy that the system uses is lost.

G-rated boilers will usually have an efficiency level of around 65%. This really shows the huge difference in efficiency between A-rated boilers and G-rated boilers.

This is one of the major reasons why having a newer modern boiler can save your home plenty of money. In 2010 new rules were brought in, which meant that all newly installed boilers must be at least 88% efficient.

Boiler Energy Ratings

Of course, there are other factors at play when it comes to efficiency. The type of model you are using can wildly affect efficiency. A non-condensing boiler will waste far more energy, which means that you will be spending far more on keeping your property warm. 

Whereas condensing boilers are much more energy efficient. It will save you huge amounts of money over its entire lifespan.

How much will a new A-rated boiler reduce my heating bills?

Annually, heating bills will cost on average between £750 to £1000. By installing a brand new A-rated condensing boiler, you can improve your heating system's efficiencies by between 14% to 34%. This is assuming that the system has been installed and set up correctly.

Replacing your home's boiler, if it is just over 10 years old, will not hugely reduce your gas bills. If it even will at all. If you find that your boiler is reliable, and has low maintenance, too, then there is very little point in ripping out the whole system and replacing it. 

However, if your boiler is old, poorly designed, and has high maintenance costs, then we would absolutely recommend replacing the unit.

A boiler that is over twenty years old will, without a doubt, be highly inefficient, and upgrading to a new modern boiler will likely save you hundreds of pounds. 

On average, in this scenario, households have been able to save upwards of £340 per year if they have a new boiler correctly installed on their property.

How to calculate your own energy bill saving:

Take a look at your yearly heating bill for the year previous. For this example, let's say it reads that the total cost is £800.

 Try to estimate the efficiency of your boiler. Use your boiler's age as a way to measure its efficiency. For this example, let's describe the efficiency as 75%.

 Now estimate the efficiency of a brand new boiler. Unless you are planning on purchasing a very top of the range model, your efficiency is probably going to rise by around 10%. So let's say that the new boiler's efficiency is 85%.

 Next, take away your existing boiler efficiency from the new boiler's efficiency. This is done to calculate what the efficiency improvement between boilers would be. In this example, the improvement is 10%.

 Finally, multiply your yearly fuel bill by the efficiency improvement. This will give you your figure for how much you will be saving per year. For this example. £800 x 0.10 = £80. So that would be an £80 saving per annum.

What is the payback period for a new boiler:

What is known as the payback period is the number of years that it will take for the upfront cost of your new boiler to be recouped through the fuel savings, bill savings, and reduced maintenance costs. 

A brand new modern boiler can end up being quite expensive.

At the lowest end of the spectrum, you should expect to pay around £1300 for a very straightforward, no-frills entry-level boiler. 

Then at the most expensive end of the scale, you have large premium boilers, which can cost you upwards of £4000.

What Is The Payback Period For A New Boiler

Then on top of that, you need to have the boiler installed. Depending on the type of boiler you have decided to go with, the installation itself can cost several hundreds of pounds. 

Getting the highest efficiencies out of your existing systems

Boiler efficiency is highly important and will bring your house all kinds of valuable savings. But heating system efficiency is even more important, plus you will find that it can cost a whole lot less to achieve better efficiency. 

If you are currently using a reliable condensing boiler, then perhaps it is worth taking a look at heating system efficiency measures.

These measures may be able to save you money, and you will not have to splash out on a brand new boiler.The best piece of advice we can give is system balancing. This process is done to ensure that all your property's radiators get to the correct temperature and give off the right amount of heat.

The balancing process involves limiting the flow of water to radiators which are nearer to the boiler in order to push more hot water in the direction of radiators which are further away.


Are you looking for new boiler installation or replacement in Southampton or Hampshire? Follow the link below for local boiler fitting by Gas Safe registered engineers.