Table of Contents
What are the best energy efficient boilers?
The most energy-efficient boilers on the market include models from Worcester Bosch, Baxi, Vaillant, Navien, and Viessmann. More details about these models can be found on this page.
When selecting a new boiler, efficiency is a critical factor to consider as it can help reduce energy costs and carbon footprint.
Energy Efficiency Regulations:
Opting for an energy-efficient boiler can lead to savings on energy bills by reducing wasted energy. Additionally, increased efficiency contributes to lowering carbon emissions.
Since April 1st, 2005, all new gas boilers installed in the UK are required by law to be condensing boilers. The same regulation applies to oil boilers since April 1st, 2007.
Boiler efficiency has gained importance due to the requirement for all boilers sold and installed in the UK to be condensing.
Boiler manufacturers are competing to enhance efficiency, technology, and innovation. They strive to utilize the latest technologies to improve appliance efficiency and brand desirability.
Online Boiler Efficiency Guide:
This page provides a detailed overview of the most efficient boilers available in the UK. Before exploring the efficiency ratings of different boilers, it’s essential to understand what Boiler Efficiency refers to.
What is boiler efficiency?
Boiler efficiency refers to the percentage of total energy used by the boiler for heating purposes.
For example, a 90% efficient boiler will utilize 90% of the supplied energy for heating your home, with the remaining 10% being lost due to inefficiency.
In practical terms, for every £1 spent on heating your home, only 10p will be wasted.
It’s important to note that a 90% efficient boiler is significantly more efficient than older non-condensing heat-only boilers, which may operate at around 70% efficiency, resulting in 30% of energy being lost.
Boiler efficiency ratings are categorized from A to G, similar to other domestic appliances. By law, all new boilers in the UK must be A-rated and compliant with Boiler Plus regulations.
| Efficiency Rating | Efficiency (%) |
| A | 90% and above |
| B | 86-90% |
| C | 82-86% |
| D | 78-82% |
| E | 74-78% |
| F | 70-74% |
| G | below 70% |
Boiler Plus Regulations
As per the UK regulations implemented in 2018, all new oil and gas boilers must be installed with a thermostat and a programmable timer.
Energy Saving Features:
Additionally, all new combi boilers must incorporate at least one energy-saving feature, such as:
- Flue Gas Heat Recovery System: Recovers heat from exhaust gases, commonly used in condensing boilers.
- Load Compensating Thermostat: Adjusts radiator temperature based on room requirements, ensuring efficiency by increasing or decreasing radiator temperature as needed.
- Smart Thermostat: Internet-compatible system allowing remote control of heating system.
- Remote Control Programming: Enables remote control of heating via smartphone or tablet.
- Smart Thermostat Features: Includes voice control, open window detection, and geofencing, accessible via handheld devices or smartphone apps.
- Weather Compensation Auto-Feature: Utilizes an outside sensor to monitor outdoor temperature and regulate boiler temperature, preventing unnecessary heating when not required.
Read about: ELECTRIC BOILERS V GAS BOILERS
Why are condensing boilers more efficient than non-condensing boilers?
Upgrading to a new condensing boiler from an older non-condensing model not only saves money on energy bills but also reduces your carbon footprint.
Condensing boilers recover heat that would otherwise be lost through the flue, thanks to a flue gas heat recovery system. This system recycles heat, preventing its loss as was common with older non-condensing models.
In condensing boilers, hot flue gases pass through a heat exchanger before being expelled through the flue outside. This process maximizes heat recovery and energy efficiency.
What boiler brand is the most efficient?
The top 5 most efficient boilers are:
1. Worcester Bosch Greenstar 24i Gas System Boiler
- 94% efficiency rating
- ErP rating: A
- Condensing: Yes
- Central Heating Max. Output: 24.6 kW
As the UK’s leading domestic boiler manufacturer, Worcester Bosch have invested heavily in the efficiency of its boilers.
The Greenstar 24i is an excellent example of this. Air uses Worcester Bosch’s advanced technologies to achieve a very high efficiency rating of 94%.
Perfect for medium sized properties
This boiler is suitable for small to medium-sized homes with up to 15 radiators.
Greenstar 24i is a system boiler with a very reasonable output of 24kW.
The excellent efficiency rating has help the Greenstar 24i to get endorsed by the Energy Saving Trust.
The WB Greenstar 24i Combi Boiler fantastic features and benefits are:
Enjoy the convenience of a spacious and user-friendly boiler control panel, designed for ease of use.
Benefit from intuitive controls that help maintain your property at your desired temperature effortlessly.
Experience energy savings with a highly efficient pump that reduces electricity consumption.
The boiler works seamlessly with a hot water cylinder, catering to the hot water demands of properties with up to two bathrooms.
Pair with the Bosch EasyControl smart thermostat for remote heating and hot water control via smartphone or tablet. Monitor energy usage and adjust heating room by room with ease.
Achieve even greater energy efficiency and cost savings by integrating with Worcester-Bosch’s Greenskies solar panels.
Rest assured with a 7-year guarantee and an A-rating for heating and hot water performance.
2. Baxi 224 Combi Gas Boiler
- 93% efficiency rating
- ErP rating: A
- Condensing: Yes
- Central Heating Max. Output: 21.8 kW
Baxi is renowned for manufacturing high-quality, cost-effective boilers that deliver excellent performance. The Baxi 224 Combi Gas Boiler exemplifies this reputation.
Being highly energy efficient, the Baxi 224 is endorsed by the Energy Saving Trust.
Ideal for smaller homes, with a maximum central heating output of 21.8 kW, it is suitable for properties with up to 10 radiators and a single bathroom.
The Baxi 224 Combi Boiler fantastic features and benefits are:
The Baxi 224 is an ideal choice for properties with limited space, thanks to its compact size.
With a high efficiency rating of 93% and an ErP A rating for heating and hot water, the Baxi 224 ensures efficient performance.
It is compatible with Baxi’s uSense smart thermostat, which complies with Boiler Plus regulations. When connected via OpenTherm, it works to reduce energy consumption and save money. uSense allows remote heating control via smartphone or tablet and learns about your lifestyle, adjusting heating accordingly with load compensation as standard.
This highly efficient boiler guarantees savings on energy bills and comes with up to a 3-year warranty.
3. Vaillant EcoTec Pro 28 kW Combi Boiler
- 94% efficiency rating
- ErP rating: A
- Condensing: Yes
- Central Heating Max. Output: 24.8 kW
The EcoTec Pro from Vaillant is a combi boiler suitable for small to medium-sized properties with up to 10 radiators and just the one bathroom.
Super Smart Technology:
The Vaillant EcoTec Pro uses super-smart technology which enables it to adapt to your heating demands and only provide you with the heat that you need. As a result, it will help you to lower your fuel bills and thus your carbon footprint.
Longer Lasting Efficiency:
The use of a stainless steel heat exchanger which offers reliability and corrosion resistance is key to this boilers energy efficiency.
The stainless steel heat exchanger will retain efficiency for longer than aluminium alternatives.
Further efficiency is achieved by the EcoTec Pro’s integration with Vaillant’s vSMART app:
The vSMART app enables you to control your heating system using an iOS and an Android app. It also has a self-learning function.
This functionality starts to understand your home’s heating needs and makes your boiler work smarter to increase efficiency and minimise your energy bills and carbon footprint.
In addition to this, vSMART features, this system has a weather compensation feature for monitoring local weather conditions and adjusts your boiler when required to ensure that your home isn’t being heated unnecessarily.
The EcoTec Pro 28 kW Combi Boiler fantastic features and benefits include:
Achieve Maximum Energy Efficiency through Innovative Technology.
Benefit from a stainless steel heat exchanger with anti-corrosion properties, ensuring prolonged efficiency.
Enjoy compatibility with a variety of wired and wireless controls, including Vaillant’s vSmart app, which enhances efficiency and learns about your home’s heating needs.
Experience automatic Weather Compensation, adjusting your home’s temperature based on outdoor conditions.
Save on running costs with a high-efficiency pump integrated into the boiler.
Convert easily to use LPG for added flexibility.
Read more: BEST COMBI BOILERS & BOILER BRANDS
4. Navien LCB700 Blue Flame 28 kW Oil Combi Boiler
- 93% efficiency rating
- ErP rating: A+ (when used in conjunction with Navien’s Smart Plus control pack)
- Condensing: Yes
- Central Heating Max. Output: 28 kW
Navien is a fairly new to the UK market having only been supplying boilers here since 2014.
They are a global leader in condensing technology and this shows with the efficiency gains provided by the Navien LCB700 Blue Flame 28 kW Oil Combi Boiler.
High Efficiency
Offering an efficiency rating of 93% and an ErP A rating for heating and hot water, the LCB700 utilises Navien’s innovative technology to achieve this high efficiency.
Key to this efficiency is Navien’s use of a blue flame burner and a stainless steel heat exchanger.
Read about: THE BEST SYSTEM BOILER BRANDS
The Navien LCB700 Blue Flame Oil Combi Boiler fantastic features and benefits are:
Navien’s SEDBUK A-rated blue flame burner incorporates revolutionary technology that replaces yellow flames in oil boilers, ensuring superior efficiency with ultra-low NOx emissions and minimal pollutant emissions.
The stainless steel heat exchanger used in the Navien LCB700 is designed to withstand corrosion and erosion, preserving the boiler’s efficiency over time.
Equipped with Intelligent Mode, the Navien LCB700 enhances efficiency by employing self-learning algorithms to monitor and adjust domestic hot water (DHW) usage according to your typical routine.
To further optimize efficiency and smart functionality, Navien offers Smart Plus controllers. These controllers enhance the LCB700’s efficiency, reduce energy bills, and minimize carbon footprint.
A Smart Plus controller enables:
- Regulation of heating based on outdoor temperature changes
- Geofencing technology to adjust heating when you’re away from home
- Operation in condensing mode for maximum efficiency
- Quick monitoring of oil consumption
Due to its outstanding efficiency, the Navien LCB700 Blue Flame Oil Combi Boiler is endorsed by the Energy Saving Trust.
In addition to other features and benefits such as:
- A high/low oil pump system allows continuous optimisation of heat/DHW output
- Built-in intelligent mode offering self-learning to increase the boiler’s efficiency based on your typical usage
- An OpenTherm ready boiler allowing for instant access to the latest control technology
- Compatibility with Navien’s Smart Plus controllers
- Navien’s industry-leading condensing technology
- A 10-year warranty
Read more: AFFORDABLE BOILER PRICES
5. Viessmann Vitodens 100-W 30 kW Combi Boiler
- 94% efficiency rating
- ERP rating: A
- Condensing: Yes
- Central Heating Max. Output: 25.4 kW
The Viessmann’s best-selling gas condensing boiler is the Viessmann 100-W.
This can be attributed to the combination of excellent reliability, efficiency and advanced technology.
Continued Investment
Viessmann’s constant investment into product development and continuous improvement has had a great effect in the efficiency of its boiler range.
The Viessmann 100-W features and benefits include:
Offering a 94% efficiency rating and an ErP rating of A for heating and hot water, the Viessmann 100-W combines high-quality components and advanced technology.
The key component utilized by the 100-W is the stainless steel Inox-Radial heat exchanger. Constructed from materials just one grade lower than surgical steel, it features self-cleaning properties and high resistance to corrosion and erosion, ensuring long-lasting efficiency.
Complemented by Lambda Pro automatic combustion control for maximum efficiency at all times, the 100-W’s MatriX-Plus cylinder burner is environmentally responsible, reducing the boiler’s CO² and NOx emissions while increasing efficiency.
This efficiency is further enhanced by the Viessmann 100-W’s smart functionality and integrated Wi-Fi, a new feature on the 2021 model.
As well as other features and benefits like:
The integrated Wi-Fi feature of the boiler makes it compatible with Viessmann’s ViCare app, allowing remote control via smartphone or tablet without requiring third-party controls.
Moreover, the ViCare app enhances efficiency by learning your daily routine, automatically adjusting heating to reduce energy consumption and lower bills. It enables specific room heating control, preventing unnecessary heating of empty rooms.
The Viessmann 100-W boasts:
- 94% efficiency rating
- ErP A rating for heating and hot water
- Advanced self-cleaning, corrosion, and erosion-resistant stainless steel Inox-Radial heat exchanger, ensuring long-term efficiency compared to aluminium alternatives
- Environmentally responsible MatriX-Plus cylinder burner, extending service life and reducing CO2 and NOx emissions
- Weather compensation technology for precise heating regulation based on outdoor temperature
- 12-year warranty
Unlike some competitors using aluminium heat exchangers manufactured by third parties, Viessmann employs stainless steel, a more efficient and durable metal.
Read about: TOP UK SYSTEM BOILERS
So Why Let’s Heat!
We fit 4 different types of boilers and heating systems!
We supply and install the following 4 different types of boilers and heating systems:
- The Common, Heat Only Boiler
- A System Boiler
- Combi Boiler
- The new Heat Pump!
If you need more info on any of these other boilers or pumps please click the links.
Finance for your boiler…
Buying a new boiler and having a boiler installation or a heat pump, is an investment.
However it can be expensive, especially paying for it all in one hit.
FCA Approved
If you haven’t got the money on hand for the boiler and installation services that you require, you can get the job done on a finance package that is FCA-approved.
We can also offer a number of split payment options for you to consider.
Boiler Replacement Payment Options
For new boiler installation, you can pay by card, pay zero deposit, and pay monthly over 2 to 10-years or take our a finance package.
So why Let’s Heat for your combi boiler replacement?
A. Let’s Heat Are Quality & Accredited Boiler Installers
Let’s Heat offers professional engineers and emergency plumbers providing reliable emergency plumbing and heating services.
Our Coverage
We provide solutions including Boiler Installation, Heat Pump Installation, Pump & Boiler Repair, and System Maintenance.
These services are available to homes and businesses in Cardiff and the surrounding CF postcode areas of South Wales. We also extend our coverage to the rest of Wales and all of England.
High Standards – 365 & 24/7
Our installation and repair team are fully qualified to the highest standards and are committed to delivering exemplary workmanship. We ensure that all boiler installation requirements are met regardless of the time or day.
Qualifications & Accreditations:
Our team of professional engineers has earned an outstanding Trustpilot score of 4.9 out of 5 from our satisfied customers.
We are fully accredited by Gas Safe and Corgi registered, and FCA approved for all financial transactions.
Experts:
All our staff at Let’s Heat are experts in their field with years of experience. They have gained expertise by working on various emergency plumbing and heating solutions and services throughout Cardiff, Wales, and the UK.
B. Because we care…
Are you still a little confused about where to start or who to use?
Our easy-to-use online questionnaire will guide you through everything that you, and we, need to know. This will ensure that you have the correct solution for your needs.
We will also ensure that you are completely satisfied with the solution offered prior to completing any works.
Why else?
Because of additional benefits like;
- Coverage of all of England & Wales.
- Reliable, professional, and trustworthy.
- High Trustpilot score of 4.9 out of 5.
- Gas Safe Accredited (corgi registered).
- Very competitive Prices.
- Finance is FCA accredited.
- Well keep your house clean and tidy during any work because we care.
- Floor protection used on each job.
- All rubbish always disposed of correctly.
- The Service comes with a 12-month snag guarantee.
You can research your boiler replacement requirements and choose your new boiler and the boiler installation online, without leaving the house…
Award winning engineers
If you’re in need of a new combi boiler or heat pump along with installation, feel free to contact our award-winning team of heating engineers. They possess all the information you’ll require.
When you’re prepared for a new boiler or heat pump, you can rely on us to provide everything you need. We’re confident you’ll be highly satisfied with our services, which encompass the full boiler supply, complete boiler fitting, and regular maintenance.
All from Let’s Heat in Wales.
Next Day Service
Next Day Service
We provide nationwide replacement and installation services for boilers and heat pumps, with next-day installation included. Orders placed before 2pm in Spring/Summer or 12pm in Autumn/Winter* are eligible.
*Please note that the cutoff time is slightly earlier in Autumn/Winter due to increased demand during these months.
Experts
Our team consists of experienced and knowledgeable professionals proficient in all aspects of heating installation, repair, and maintenance services.
For any further inquiries, please don’t hesitate to contact us.
Alternatively, feel free to explore our FAQs or blog for additional information.
Full range of heating & plumbing services provided by Let’s Heat:
- Boiler Repairs & Installations
- Boiler Supply & Fit
- Financing Your Boiler
- Emergency Boiler Repairs & Installations
- Emergency Boiler Supply & Fit
- Plumbing Repairs
- Bathroom Plumbing
- Kitchen Plumbing
- Emergency Plumbing Repairs
- Bathroom Plumbing in Emergencies
- Emergency Kitchen Plumbing
- General Plumbing Services
- Emergency Plumbing Services
- Emergency Gas & Heating Engineer
Any more questions?
If you have any further inquiries regarding boiler efficiency, other boiler options, or any other topics, please refer to our FAQ Page, where you may find the answers you seek.
Alternatively, you can explore our News Blog for a wealth of articles covering various aspects of plumbing and heating.
Visit our Gas Safe Registration to ensure compliance, and check out our near 5-star Trustpilot rating by clicking the relevant link to find what you’re looking for.
Don’t miss out on our exceptional value-for-money offerings! Get a quote today!
Read more about:
What is a combi boiler and How They Work?
FAQ’s
What type of boiler is cheapest to run?
Generally speaking, gas boilers are less expensive to run.
Is a high efficiency boiler worth getting?
A high efficiency, gas-fired condensing boiler is among the best economical and clean ways to heat your home, reduce your heating bills, and finally lessen the impact on the environment.
What is a good efficiency rating for a boiler?
The AFUE rating for an all-electric furnace or boiler is between 95% and 100%.
How much does an energy efficient boiler cost?
the cost of a boiler varies between £500 – £2,500, depending on the system, size and model.
How long do high-efficiency boilers last?
around 15 years.
