Most Energy Efficient Boilers 2023 Re January 20, 2023

Most Energy Efficient Boilers 2023

A-Landlords-Guide-to-Saving-on-Energy-Bills

Before we jump into this blog, we know that there is a lot of confusion around what is happening with the Gas Boiler Ban which is due to take place as soon as 2025, meaning that a lot of us have been left unsure about whether buying a new boiler is the best option.

If you want to hear about the way we feel things are going, we have a separate blog that explores this. Head over to our ‘Will Hydrogen Boilers or Heat Pumps Replace Gas Boilers?’ blog for more information.

A lot of us will check the ErP Rating label of our boilers and as long as they’re above a B-rating, we’re happy with it. However, a lot of us forget that the efficiency of your boiler can depend on a number of factors such as whether your boiler is a condensing or non-condensing unit, the age of your boiler, whether your boiler’s kW size is compatible with your homes needs and demands, how many people are using the heating system at one time etc.

This blog will discuss not only the top three most efficient combi boilerssystem boilers and regular boilers on the market, but will also let you in on a few secrets about how to ensure that your boiler is working as efficiently as it should and keeping your home nice and warm this winter. And of course, to help you save money on your heating bills.

Before we start, here is a little information about how each boiler type works. This may help you to identify which type of boiler you have installed in your home. If you are looking for more in-depth information about different boilers types, then we have a separate blog on these.

Boiler Types

Combi boilers

Combi boiler heats water as you need it, ideal for smaller homes.

System boilers

Like a heat-only boiler but more components are built-in, meaning they take up less space and you don’t need a cold water feed tank in the loft.

Regular boilers

A regular, heat-only system means you will have a cold water feed and hot water tank where hot water can be stored for later use. They’re ideal for larger properties.

According to the Energy Saving Trust (2021), condensing boilers are 25% more efficient than non-condensing boiler units. If you have an old non-condensing boiler, upgrading to a newer condensing unit could potentially save you between £45 and £300 on your annual bills.

Regardless of the boiler that you choose, by upgrading your boiler to a new condensing boiler, you will see immediate changes in the cost of your energy bills. Condensing boilers work to recover heat that a non-condensing boiler would have lost via the flue. 

This is called a flue gas heat recovery system and works by recovering heat by recycling exhaust gases (mostly hot steam with some acidic content) that older non-condensing used to waste. In condensing boilers, the hot flue gases go through a heat exchanger first before they exit through the flue outside.

How Boiler Energy Efficiency Ratings Work

All modern boilers are rated for efficiency under the European energy label ErP which stands for ‘Energy-related Products’ which was introduced in 2015. It rates boiler efficiency from A+++ to F, the A+++ being the most efficient boiler you can get. 

Combi boilers have two ratings: space heating (the letter under the radiator symbol) and water heating (the letter under the tap symbol).

Space-heating refers to how efficient your boiler is at heating your radiators, while the water heating component is how efficient a combi boiler is at heating your hot water for showers and taps. 

System and Regular boilers only have the space-heating part of the ErP label.

The ErP label also shows boilers sound power level measures in decibels (dB). The higher the number, the louder the boiler is while operating. If you are looking for a quiet boiler, we have a blog that covers the top 5 quietest boilers on the market. 

Finally, as you can see from the image above, the ErP label also shows the boilers heating output in kW. If you’re not sure what kW means when it comes to your boiler, we cover this in a separate blog, so head over and give that a read. Once you’re done here, of course 😉.

Nearly all modern gas condensing boilers available in the UK get an A rating on this label. The UK government introduced ‘Boiler Plus’ legislation in 2018, which now requires all boilers to have a minimum ErP efficiency of 92% (or A-rated).

SEDBUK Efficiency Rating

SEDBUK stands for Seasonal Efficiency of Domestic Boilers in the UK. If you are interested in the minutiae of how one boiler’s efficiency compares to another, we would suggest looking into the SEDBUK 2009 efficiency rating. The SEDBUK 2009 is a system that is used to classify and compare boilers specifically, on how efficient they are at converting fuel into heat.  

Traditionally, SEDBUK ratings were shown on labels as a letter, but these letter labels have since been withdrawn to avoid confusion with the ErP labels, which use similar ratings but have different meanings. The SEDBUK 2009 is used to rate the energy efficiency of boilers specifically, whereas ErP Ratings are used for all energy appliances. 

There are currently two different types of SEDBUK ratings, (also referred to as SAP scores) that you should look out for when you are buying a boiler. 

SAP winter efficiency – this is measured by an independent laboratory and is the efficiency of the boiler including space heating and hot water. There are only marginal differences between modern condensing boilers on this measure.

SAP hot water efficiency – this figure measures how efficient the boiler is at producing hot water for your taps. There tends to be a much bigger difference between boilers on this measure, so if you are keen to get the most efficient boiler possible, this figure that you should hone in on.

How is Boiler Efficiency Calculated?

There are a few different ways you can check the efficiency of a boiler. The most obvious way is to check its SEDBUK (Seasonal Efficiency of a Domestic Boiler in the UK) rating, which is always displayed as a percentage – the higher the percentage, the better. As mentioned, from April 2018, the Government have announced that all boilers that are installed in the UK must have an EPR rating of 92%.

Boiler Efficiency Ratings

In the same way as other domestic appliances sold in the UK such as fridges, freezers and washing machines, boilers are rated using an energy efficiency rating scheme from A-G. However, to comply with UK law’s and the Boiler Plus regulations, all condensing boilers sold in the UK are required to be A-rated.

The energy efficiency rating scheme can be seen below:

Efficiency RatingEfficiency (%)
A90% and above
B86 – 90%
C82 – 86%
D78 – 82%
E74 – 78%
G70% and below 

 

How does Energy Efficiency Translate into Money?

As mentioned at the beginning of the blog, replacing your non-condensing boiler with a modern, condensing boiler, can save you up to £300 on your annual energy bills. 

If you have an older, non-condensing boiler that has an efficiency rating of 85% (which would be a C-rated energy efficient boiler), for every £1 you spend on energy to heat your home, 15p of that £1 is being wasted. That may not seem like a lot, but when you start to notice that for every £100 that you spend on energy, you started off losing £15, which over the years has increased to £30 (at 70% efficiency), and £50 (at 50% efficiency) lost simply due to a boiler operating at low efficiency, it all starts to add up. 

New condensing boilers start off at 90% energy efficiency and can climb up to 92% to 94% efficiency with the help of programmable thermostats or smart, internet-enabled thermostats and weather compensation.  That’s only £8 or £6 lost on every £100 spent on energy.  Which is a lot less.

Then you have high-end, top-of-the-line, premium condensing boilers like the Viessmann Vitodens 200-W system boilers that go up to a jaw-dropping 98% efficiency.  Even 100% in some cases by recycling outside air and by always being in condensing mode.  The money lost there is £2, or none at all!

This means that you could be saving up to £500 on your annual energy bills purely depending on the efficiency rating of your boiler.

Energy Efficiency Annual Savings For Different Properties

Semi-Detached Property

Boiler Rating

Annual Savings

D (79% – 82%)

£120

E (74% – 78%)

£120

F (70% – 74%)

£140

G (less than 70%)

£200

Detached Property

Boiler Rating

Annual Savings

D (79% – 82%)

£180

E (74% – 78%)

£180

F (70% – 74%)

£210

G (less than 70%)

£305

Mid-Terrace Property

Boiler Rating

Annual Savings

D (79% – 82%)

£105

E (74% – 78%)

£105

F (70% – 74%)

£120

G (less than 70%)

£175

Detached Bungalow Property

Boiler Rating

Annual Savings

D (79% – 82%)

£90

E (74% – 78%)

£90

F (70% – 74%)

£105

G (less than 70%)

£155

Most Energy Efficient Combi Boilers on the Market

With the help of our new Boiler Comparison tool, we are able to compare up to 3 boilers at once, to help us identify the most efficient combi boilers on the market.

Now that we’ve covered everything you need to know about the importance of choosing an energy-efficient boiler, let’s get into the top three energy-efficient combi boilers. 

Worcester Bosch Greenstar 4000 Combi Gas Boiler

worcester-bosch-4000

Which? Brand Score: 84%
kW Outputs Available: 25kW 30kW 
Efficiency Rating: 94%
ErP Rating: A
Condensing Unit: Yes

Boiler Features:

  • Quick Tap water-saving function 
  • Easy access to all areas for easy servicing 
  • Full-text colour display LED screen
  • Reduced risk of freezing with siphonic release 
  • Quieter operations (45dB) 
  • C6 heat exchanger and improved modulation 
  • Reminder settings, fault history and drain-down function
  • Easy access to drain valve and pressure gauge 
  • Auto-filling features
  • Ability to reduce gas consumption
  • 100% planet-friendly packaging 
  • Simple Switch option

Viessmann Vitodens 100-W Combi Gas Boiler

vitodens 100-w

Which? Brand Score: 81%
kW Outputs Available: 19kW 25kW 32kW
Efficiency Rating: 94%
ErP Rating: A
Condensing Unit: Yes

Boiler Features:

  • Frontal access to the boiler for easy maintenance 
  • An Inox-Radial heat exchanger with an extended 10-year warranty 
  • Optional Vitotrol 100 controls
  • 7-day timer
  • Easy to use controls 
  • Backlit LCD touch-screen display

Vaillant EcoTec Pro Combi Gas Boiler

vaillant-ecotec-pro

Which? Brand Score: 76%
kW Outputs Available: 24kW | 28kW 30kW
Efficiency Rating: 94%
ErP Rating: A
Condensing Unit: Yes 

Boiler Features:

  • Removable side panels 
  • A low NOx burner 
  • Built-in frost protection for extra peace of mind 
  • Stylish contoured case design with down flap 
  • Easy to use controls 
  • Easy to read display screen 
  • Quiet operation

Most Energy Efficient System Boilers on the Market

Viessmann Vitodens 200-W System Gas Boiler

vitodens 200-w

Which? Brand Score: 81%
kW Outputs Available: 11kW 19kW | 25kW | 32kW 
Efficiency Rating: 98%
ErP Rating: A
Condensing Unit: Yes 

Boiler Features:

  • Touchscreen display for easy use 
  • Stainless steel Inox-Radial heat exchanger 
  • MatriX Plus burner installed
  • Optional WiFi controls
  • Built-in frost protection 
  • User-friendly controls 
  • Suitable for integration of a solar thermal system
  • Up to 98% of the fuel that is used to convert it into heat

Worcester Bosch Greenstar 8000 Style System Gas Boiler

WB Style black 30kw

Which? Brand Score: 84%
kW Outputs Available: 30kW 35kW 
Efficiency Rating: 94%
ErP Rating: A
Condensing Unit: Yes 

Boiler Features:

  • Modulation ratio of 1:10

  • Increased power over previous Worcester Bosch boilers
  • Compatibility with intelligent and smart technology 
  • Greenstar intelligent filling system to ensure optimum pressure 
  • Built-in frost protection for peace of mind
  • Easy to use controls 
  • Easy to read display screen

Ideal Logic Plus System Gas Boiler

ideal-logic-heat

Which? Brand Score: 74%
kW Outputs Available: 15kW 18kW 24kW | 30kW
Efficiency Rating: 93%
ErP Rating: A
Condensing Unit: Yes 

Boiler Features:

  • Built-in frost protection for extra reassurance 
  • A large digital LCD display screen for easy use
  • User-friendly heating controls
  • A low lift weight for easy installation
  • Scratch-resistant casing
  • Compact design 
  • LPG conversion kit is available for off-grid properties

Most Energy Efficient Regular Boilers on the Market

Worcester Bosch Greenstar Ri Regular Gas Boiler

Worcester 27RI and 30RI

Which? Brand Score: 84%
kW Outputs Available: 12kW 15kW 18kW | 21kW | 24kW | 27kW | 30kW
Efficiency Rating: 92%
ErP Rating: A
Condensing Unit: Yes 

Boiler Features:

  • Aluminium and silicon heat exchanger 
  • Easy to use controls for maximum comfort 
  • Built-in frost protection for extra peace of mind
  • Easy to read display screen 
  • Compatible with the Greenskies solar panels

Vaillant EcoFit Pure Regular Gas Boiler

vaillant-ecofit-pure

Which? Brand Score: 76%
kW Outputs Available: 12kW 15kW | 18kW | 25kW | 30kW | 35kW
Efficiency Rating: 94%
ErP Rating: A
Condensing Unit: Yes 

Boiler Features:

  • Quiet operation 
  • Aluminium heat exchanger
  • Automatic temperature setter
  • Rear flue option
  • Built-in frost protection for extra peace of mind in those colder months
  • Easy to use controls
  • Easy to read display screen 

Baxi 600's Regular Gas Boiler

baxi-600

Which? Brand Score: 76%
kW Outputs Available: 13kW | 16kW | 19kW | 25kW | 30kW 
Efficiency Rating: 93%
ErP Rating: A
Condensing Unit: Yes 

Boiler Features:

  • Fitted with an Adey Micro2 compact system filter to greatly reduce the chance of a fault developing 
  • Quiet operation
  • An easy to read digital display screen
  • Easy to use controls for maximum control and comfort in your home
  • Built-in frost protection 

How To Maintain The Efficiency of Your Boiler

Many of us will have our own little ways to save money on our energy bills. Some will actively put money aside each month for it, while others will stubbornly avoid putting the heating on until you can physically see your breath in front of you (we all have that one family member!). However, one of the best ways you can save on your energy bills is through your boiler. While boilers are one of those home necessities that we hate to spend money on, investing a little time to ensure it’s running to maximum efficiency is one of the best ways to keep the costs down. Here are some top tips on how to keep your boiler as efficient as it can be: 

Regular Servicing

Getting your boiler services annually is very important. Getting your boiler serviced will mean any potential problems can be identified and fixed sooner rather than later, which will save you money and a lot of hassle in the long run. Serciving your boiler is vital in keeping you and your family safe from potential carbon monoxide poisoning

Turn Your Heating On

Believe it or not, making the point of switching your heating on during the warmer months is actually a good way to keep your boiler running smoothly. Think of it like a car – if you don’t use it for months on end and suddenly go to switch it on on a chilly morning, it’s far more likely to seize up. You don’t have to go mad during the warmer months, just pop the heating on once a week to make sure that things are ticking over nicely.

Keep it Clean

It’s easy to overlook your boiler when you’re cleaning your home, but keeping it dust-free is one measure you can take to keep things running efficiently. If dust builds up, this can clog up tubes and pipes which not only can affect its performance but can also result in higher energy bills too.

It is recommended that you have a system flush during a boiler installation to flush out any built-up dirt and rust in the pipework and radiators left behind from the old boiler. Your Gas Safe engineer will be able to access your system and perform this fairly simply. 

If you buy a new or replacement boiler from WarmZilla, a system flush will be performed with every installation. We also add an inhibitor at the end of your boiler installation to keep the system coated to reduce corrosion, limiting the amount of debris and rust that builds up.

Bleed Your Radiators

If the radiators in your home are colder at the top than at the bottom, this usually means that your heating isn’t running as efficiently as it could be. By bleeding your radiators, you’re releasing any air that’s become trapped in the system, preventing it from becoming fully heated. It’s a simple task that takes just a few minutes and can be done by yourself, but in the long run, it could save you a fair few quid. 

Check Your Water Pressure

Loss of pressure in your boiler can be responsible for a number of issues, so it’s important to regularly check and top it up if needs be. Simply check the pressure gauge on your boiler, and as a rule of thumb, anything around the 1.5 mark is healthy, although every boiler is different so it’s worth checking your manufacturer’s guide just to be safe. In most cases, you can repressurise your boiler yourself, but it’s always best to consult your manual first in case it needs to be done by a Gas Safe Engineer.

Insulate Your Pipes

Insulating your central heating pipes with easy-fit foam lagging (which you can buy from most DIY stores), will reduce the amount of heat loss, meaning water stays hotter for longer. In turn, your boiler won’t have to work quite as hard, meaning you’ll save a little more on those energy bills.

Consider a New Boiler

If you’ve tried every which way to maximise your boiler’s efficiency and you still don’t see an improvement to the cost of your bills, it may be worth considering if it’s time to invest in a new one.

At WarmZilla we want to make it super easy for you if you decide to go for a new boiler, which is why you can get a quote online within minutes. Whether you opt to go for a flexible finance package or pay in full too, there’s even more ways for you to get a brand new boiler at an affordable price. 

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