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What is an efficient boiler and why should I want one?

With everything going on in the news about gas prices, and with COP 26 just around the corner, we’re willing to bet that you’ve got some questions about boiler efficiency, and how you can save money. Don’t worry, The Heating People are here to help! In this blog we’ll explain what boiler efficiency is; how it can save you money (as well as the planet); and how this fits into the bigger picture on climate change.

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What is an efficient boiler?

With everything going on in the news about gas prices; and with COP 26 just around the corner; we’re willing to bet that you’ve got some questions about boiler efficiency, and how you can save money.

Don’t worry, The Heating People are here to help!

In this blog we’ll explain what an efficient boiler is; how it can save you money (as well as the planet); and how this fits into the bigger picture on climate change.

What is climate change?

Unfortunately, as a result of human activity, the world is getting hotter. When we burn fossil fuels for energy, carbon dioxide and other greenhouse gases are emitted into the atmosphere.

These gases act like a blanket around the planet, trapping the heat from the sun. This causes global temperatures to rise, resulting in long-term changes to the climate.

Since the Industrial Revolution, the average temperature of the planet has risen by around 1°C. The IPCC says that to avoid the most catastrophic impacts of the climate crisis; we must limit global warming to below 1.5°C.

In November 2020, the government published ‘The Ten Point Plan for a Green Industrial Revolution’. This report outlines how the government envisages meeting its ambitious target of net zero carbon emissions by 2050. You might have seen this on the news in relation to electric vehicles and heat-pumps.

What do boilers have to do with climate change?

We are dependent on our boilers to keep us warm and comfortable all year round; and to keep up with our demands for hot water.

But in order to produce heating and hot water for us, boilers need to burn fuel, usually gas.

Unfortunately, the by-products of burning the fuel are damaging to the environment. And that’s where an efficient boiler comes in.


What is boiler efficiency?

An efficient boiler needs to use the least amount of energy to keep your house warm, and your water hot.

When we’re talking about using energy here, what we’re really talking about is fuel.

An efficient boiler needs to burn less fuel (usually gas) to keep you comfortable.

An inefficient boiler does the opposite. It burns loads more fuel to do exactly the same job; which makes it more expensive to run; and worse for the planet.

In the past, boilers burned their fuel inefficiently; because they didn’t have the condensing technology and other energy saving devices that we have today.

And many homes still have these old inefficient boilers; which are burning more gas than they need to; and are therefore releasing excessive amounts of gas into the atmosphere.

Modern boilers burn their fuel very efficiently; but will inevitably still lose some heat energy; and emit some flue gases in the process.

Other factors such as oversizing a boiler will further reduce boiler efficiency.

This is why it’s vital to get a competent installer for your boiler replacement. Counting radiators to determine boiler size simply doesn’t cut it.

The Heating People use heat loss calculations as standard to determine the most efficient boiler for your needs.

How does boiler efficiency impact my heating bills?

Boiler efficiency refers to the percentage of the total energy used by the boiler; to provide your heating and hot water. As we’ve mentioned, no boiler is 100% efficient, some heat will always be lost.

To put this into context…

An old inefficient boiler with 73% efficiency will use 73% of the supplied energy for heating your home; but the remaining 27% of energy will be lost. So this means that for every £1 you spend on heating your home, 27p is wasted.

According to The Energy Saving Trust, you could save as much as £340 a year on your gas bill; if you’re trading in an old-style non-condensing boiler for a new condensing one.

Check out our related blog: Does smart heating save money?

How has Boiler Plus improved boiler efficiency?

Diagram showing Boiler Plus.The Boiler Plus legislation was introduced in 2018 to improve the way we use energy in our homes.

Boiler Plus has improved the efficiency of boilers by requiring condensing technology as standard.

When you buy a new boiler, you know it’ll be at least 92% efficient; as opposed to the old G rated boilers; which could be just 70% efficient; or sometimes lower!

It requires that all new boilers must now have a minimum ErP (Energy related Products) rating of 92%. And all gas and oil boilers must have appropriate time and temperature controls fitted.

It also requires combi boilers to have one of four additional energy saving devices fitted:

Flue Gas Heat Recovery (FGHRS)

Cycling arrows.This is a system that enables the boiler to reuse heat that would have otherwise been wasted.

Weather Compensation

Weather compensators allow the flow temperature to be modulated based on the outside temperature.

Load Compensation

Load compensation allows the flow temperature to be modulated from the boiler based on room temperature.

Smart controls with automation and optimisation functions

‘Smart’ stands for “Self-Monitoring Analysis & Reporting Technology”, and covers a large group of controls.

Smart controls can often connect to the internet and can be controlled remotely through a tablet or smartphone. This means that you have much greater control over your heating, from wherever you are, at any time of day.

There are a huge variety of options available with smart controls, such as zoning, geo-fencing and intelligent learning systems.

What is a condensing boiler?

There’s a common misconception that a ‘condensing boiler’ is a type of boiler, when in fact, it isn’t.

The terms ‘condensing boilers’ and ‘non-condensing boilers’ are misleading. They actually describe the technology within the boiler itself, rather than what sort of boiler it is.

Thanks to Boiler Plus, all new boilers must have condensing technology as standard.

This is because condensing boilers are more energy efficient than their non-condensing counterparts. They can typically extract 90-92% of heat from fuel; compared to 50-80% that a non-condensing boiler can.

A condensing boiler works by recycling the wasted exhaust gas that is created during a boiler’s normal operation.

By re-using the exhausted gas; water vapour and steam back through the system; some of the heat and water is retained making the boiler’s operation more efficient.

But you don’t need to worry about choosing condensing technology, all new boilers come with this.

How can I tell how efficient my boiler is?

The easiest way to check the efficiency of a boiler; whether it’s one you already have; or one you’re thinking of getting; is to look at its efficiency rating.

There are currently two ways of rating a boiler for efficiency: ErP and SEDBUK.

What is ErP?

All modern boilers are rated for efficiency under the European energy label introduced in September 2015.

ErP stands for ‘Energy-related Products’. This rating system was designed to drive improvements in the efficiency and performance of heating and hot water. It means that you can see how efficient your appliances are.

Under this scale, boilers are rated from A-G, with A being the most efficient, and G being the least efficient.

If you have an old boiler, it might be low on the scale, indicating the need for a replacement.

Since most modern boilers in the UK now get an A rating on this scale; the SEDBUK 2009 efficiency rating is also useful.

What is SEDBUK?

SEDBUK stands for Seasonal Efficiency of Domestic Boilers in the UK.

The system was developed by boiler manufacturers and the UK government to enable a fairer comparison of the energy efficiency of boilers.

Although it’s been replaced by ErP, many boiler manufacturers still put the SEDBUK efficiency in their product catalogues.

This is because most modern boilers will be A rated on the ErP system; but SEDBUK allows you to see the percentage detail.

What are the potential savings from a more efficient boiler?

Heating accounts for about half of what you spend in a year on energy bills. So an efficient boiler can make a big difference to your bills.

The Energy Saving Trust says that you could save as much as £340 a year on your gas bill with a new, efficient boiler.

But the savings are likely to be bigger than this now, given the current price of gas!

But just because your boiler is A-rated out of the box; doesn’t mean it will be in your home; if it’s the wrong size; has sub-standard controls; or isn’t installed right.

In these situations your new boiler will run well below its A-label efficiency rating.

This is why you need a skilled installer to maximise the efficiency of your heating system.

How do I make sure that my boiler reaches its efficiency potential?

If you’ve decided to replace your old boiler with a newer; more efficient model; there are a number of things to think about to ensure that it can reach its full energy saving potential:

An efficient boiler needs to be installed by an expert

A heating system will only be as good as its design and setup.

You can have the most efficient boiler on the market; but if it’s the wrong size or poorly set up; it’ll run below its efficiency capability.

Rest assured that The Heating People are boiler installation specialists who offer a bespoke service to ensure that your boiler is as efficient as possible.

An efficient boiler must be the correct type of boiler for your home

The first step in getting an efficient heating system; is to choose the correct type of boiler for you and your family.

There are three types of boiler available: heat-only or conventional boilers; combination or ‘combi’ boilers; and system boilers.

The different types of boiler lend themselves to different sizes of home and different demands for hot water.

If you’re generally happy with what your old boiler offered when it was working well; then a replacement boiler similar to the old one could be a good option.

But you shouldn’t automatically assume that you need the same type of boiler that you’ve had previously. Lots of circumstances have probably changed since your old boiler was installed. And it might not have been the best choice years ago, when it was first installed.

During your free survey with The Heating People; we’ll ask you about how you currently use your heating and hot water; to check that you have the correct type of boiler for your needs.

An efficient boiler must be sized correctly

A calculator next to a thermal image.As well as being the correct type of boiler; your boiler also needs to be the correct size for your needs.

Boiler size doesn’t refer to the physical dimensions of the appliance itself; but rather how much energy is output by the boiler in terms of heat; which is measured in kilowatts (kW).

So each model of boiler will come in a range of sizes, or power outputs to suit different lifestyles.

If you choose a boiler that’s too big, you’ll be wasting energy and paying over the odds on your bills.

But if it’s too small, it might not be powerful enough to heat your home, or give you enough hot water.

So, you’re facing the Goldilocks conundrum of finding a boiler that’s ‘just right’.

And this is where a lot of people (and installers who don’t know what they’re doing) go wrong. They oversize the boiler, ‘just in case’.

But if you choose a larger boiler that has a much higher capacity than you need, you’ll be wasting money not only on the initial purchase, but also on escalating energy bills.

Oversized boilers heat up too quickly; run for a short time; and then will turn off; before the cycle starts again.

This constant stop-starting, or ‘boiler cycling’ prevents the boiler from operating in its ‘sweet-spot’ or condensing mode, and makes it inefficient.

Most UK homes only need about 6-8kW of power output from their boiler on a very cold day. Yet, some boiler manufacturers are boasting about their 50kW boilers. This just plays on the common misconception that bigger is better. It certainly isn’t when it comes to boiler size!

But you don’t need to worry about choosing the correct size, The Heating People will do this for you.

We’ll conduct a heat loss calculation to find the correct size boiler for your needs.

This is Industry best practice under Regulation L of the Building Regulations 2010, but it’s surprising how many installers don’t bother.

If an installer wants to recommend a boiler based on how many radiators you have – RUN!

An efficient boiler must be part of a balanced system

In order for your boiler to operate as efficiently as possible, all of your radiators need to be emitting the right amount of heat. This is where system balancing comes in.

Balancing involves restricting the flow to radiators nearer to the boiler in order to push the hot water along to radiators that are further away.

This helps make sure that all of your radiators are getting hot, and that the temperature of the water that’s returning to the boiler is 50 degrees or lower, so it can work in its efficient condensing mode.

An efficient boiler must be part of a clean system

You can’t install a shiny new boiler into a filthy system of corroded pipes and radiators, and expect to get high efficiencies out of it. In order for our heating systems to work well, they need to be clean.

Over time, the water in your pipes, boiler and radiators deposits unwanted by-products like rust.

This rust (plus other dirt and debris) becomes an unpleasant, muddy substance, known as ‘sludge’. This sludge plays havoc with the efficiency of your heating system, causing corrosion and blockages.

A report by the Department for Business, Energy and Industrial Strategy (BEIS) in February 2021 found that the build-up of sludge can reduce the efficiency of central heating systems by by 15%.

This is why it’s a very good idea to have a power flush when installing a new boiler.

A power flush is a cleansing process which cleans your entire central heating system, removing the sludge, which would otherwise cause damage and reduce efficiency.

The Heating People are able to offer this service alongside your boiler replacement, so you know you’ll be getting the most out of your new boiler.

An efficient boiler must be paired with good heating controls

Heating controls are a vital part of your heating system because they allow you to keep your home at a comfortable temperature without wasting fuel or heat.

There are a wide range of heating controls available that will help your heating system work more efficiently and help keep your bills down.

According to the Energy Saving Trust, you can save £70 and 300kg of carbon dioxide a year by installing and correctly using a programmer, room thermostat and thermostatic radiator valves.

You should also consider investing in smart controls. Smart heating controls can often connect to the internet and can be controlled remotely through a tablet or smartphone.

This means that you have much greater control over your heating, from wherever you are, at any time of day.

There are a huge variety of options available with smart controls, such as zoning, geo-fencing and intelligent learning systems.

This gives you smarter control of your heating, remote access, and the promise from manufacturers of energy savings of between 20-30%.

The Heating People will be able to advise you on the best options for your central heating system.

An efficient boiler must be serviced annually

An engineer conducting a boiler service.To keep your boiler working as it should, and to maximise its life span (not to mention ensure that it stays safe) you need to get it serviced annually by a Gas Safe engineer.

During your boiler service, your engineer will clean up any deposits that have built up in the boiler.

Ensuring that the internal combustion areas are free of dirt and debris will improve the heat transfer, allowing your boiler to light more easily and burn efficiently, which can lead to lower heating bills.

Final thoughts…

Once you’ve got an efficient boiler and your system is set to maximise its efficiency potential, keep in mind that there are other things that you can do to further improve efficiency.

We have other blogs dedicated to this topic, so we’ll just leave you with these two top tips:

Turn your thermostat down by 1 degree

According to the Energy Saving Trust, this one simple tip could reduce your energy bills by around £80 a year. But maybe you’d be comfortable turning it down by more than one degree?

Why not try turning your heating controls down until you find the best thermostat temperature for your comfort levels, and your wallet!

Check your insulation

When your central heating’s on, you want it to be warming you up, and not your garden!

According to the Energy Saving Trust, a poorly insulated house will lose up to 25% of its heat through the roof; 35% through the the outside walls; 25% through the doors and windows; and 15% through the ground floor.

So to keep you warmer for longer, and therefore minimise your energy usage, you should install insulation or thicken what’s already there.

The Energy Saving Trust say that with decent loft insulation, you could save between £120 and £225 a year, and filling your cavity walls could save you between £70 and £255 a year.

We hope you’ve found this blog useful. If you want some help finding a more efficient boiler for your home, contact one of our friendly team today.

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