What’s The Most Energy Efficient Boiler?

Going for a brand new A-rated combi boiler could be the best thing that’s ever happened to your energy bills, because according to the Energy Saving Trust, you could trim off an amazing 40%!

The Energy Saving Trust is a useful resource for learning how to reduce your carbon footprint

In this article you’ll find factual and trustworthy information for when you purchase your new boiler, as well as learning a thing or two about energy efficiency along the way!

How can I improve energy efficiency in my home?

Every home needs to be comfortable heated!

It’s all well and good telling someone a new boiler will improve their home’s efficiency, but there are still things that can be done in the meantime to help out.

Long Term Improvements:

Short Term Improvements:

  • Have thick curtains fitted
  • Have a programmable thermostat installed
  • Replace other appliances with more modern, more efficient models
  • Add insulation to doors and windows
  • Switch energy provider for lower cost option

You may think ‘switch to a new condensing boiler’ is a fairly obvious point to make, but we’ll be going through that in a bit more detail later on.

Cavity wall insulation is useful in storing heat and saving you money

We’ve mentioned ‘Cavity Wall Insulation’ in the list above, but how does it actually help? Studies suggest around 35% of heat loss from typical homes escapes via external walls. So for every square metre of insulation fitted, you can save over a tonne of carbon dioxide during the average building’s life.

Now let’s move onto the biggest point of curiosity…energy efficient condensing boilers!

Why should I get a new condensing boiler?

Why should I get a new condensing boiler?

If your boiler’s around 12-15 years old, it’s a condensing boiler. There are many condensing boilers older, but most will be non-condensing, which has its own detriments.

Non-condensing boilers are unable to recycle the waste gases produced while operating, so any chance to reuse heat from these gases, is lost. This is where condensing boilers win the contest.

Condensing boilers use modern technology to ensure hot gases passing through the heat exchanger get reused for heating water returning from radiators. What does this mean in the long run? There’s not as much energy wastage, so lower energy bills!

How does an energy efficient condensing boiler save me money?

Technology is always advancing, meaning manufacturers are always finding ways for you to save money.

In the world of boilers, energy efficiency means less fuel is used to produce the same results. Typical non-condensing boilers start off at around 85%, but daily use and thermal stress can bring it down to 50-70%.

People sometimes get confused between combi and condensing boilers, but any combi installed within 15 years will be condensing. The ‘Combi’ part refers to the boiler type, but other examples include open vent, system and storage combi boilers.

How does that work with money?

how can you save money with a new boiler?

Let’s use the previous example of 85% efficiency. For every £100 you put towards your heating, you’d be wasting £15. Spread this over a full year with seasonal changes, and you could be looking at more.

New condensing boilers normally start in the early 90 percentile,  but largely depends on which boiler you end up with.

Besides individual brands such as Viessmann and Ariston known for their efficiency, there are other ways to upgrade your boiler’s efficiency, like smart thermostats, weather compensation technology and power flushes. Efficiency can be boosted to 92-94%, but in monetary terms, for every £100 spent on heating, you’d lose £6-£8 a year. Not that much at all!

The boiler’s overall efficiency largely depends on the brand you end up choosing. In terms of percentile, you can’t go wrong with the Viessmann Vitodens 200-W boiler, boasting an amazing 98% efficiency.

Translating these numbers into savings, you could be taking as much as £500 off your annual energy bills! There’s a lot of ways you can treat yourself with that kind of money!

What’s the most energy efficient combi boiler?

Let’s see what’s current on the market for most energy efficient combi boiler:

  1. Viessmann Vitodens 200-W Combi

The Viessmann Vitodens 200-W Combi is an excellent example of efficiency

The Viessmann Vitodens 200-w Combi is absolutely the most energy efficient combi boiler you can currently buy on the market.

Viessmann have many years experience in commercial heating, and have boilers in many famous landmarks, including Cardiff’s Millennium Stadium!

They eventually made the wise decision to enter the domestic market, and they brought one of the best boilers out there with them.

The Vitodens 200-W operates at an efficiency level of 98%, but combines weather compensation and quality materials to achieve this.

Main benefits of the Viessmann Vitodens 200-W:

  • 98% efficiency, one of the best levels in the industry
  • Operates at a volume of 34db, working quietly in the background
  • Inox-radial stainless steel heat exchanger
  • Control through mobile phone or internet connection (with optional Vitoconnect 100W LAN adaptor)
  • Small, compact shape (450mm wide)
  • Energy efficiency rating: A
  • No need for extra LPG Conversion Kit
  • MatriX cylinder burner


  1. ATAG iC Economiser Plus 35 Combi

ATAG originate from the Netherlands, and have made a strong impression among the heating and boiler industries. They’re a strong contender in the efficiency race with levels at 94% and above.

Main benefits of the ATAG iC Economiser Plus 35:

  • Pre-heat capabilities allow instant hot water
  • Passive Flue Gas Heat Recover Device built-in
  • Built-in outside weather compensation technology
  • ErP Rating: A
  • Compact size
  1. Viessmann Vitodens 100-W Combi

The Vitodens 100-W is one of Viessmann’s best selling condensing boilers in the UK and Europe.

Main benefits of the Viessmann Vitodens 100-W Combi:

  • Compact shape and design
  • Quiet operation with low fan speed
  • Inox Radial Stainless steel heat exchanger
  • Output availability ranges from 4.7 to 35KW
  • Energy Efficiency rating: A
  • Lowered environmental impact and reduced carbon footprint
  • Backlit LCD Touch Screen for easy access
  1. Vaillant ecoTEC exclusive with Green iQ combi

Vaillant state that 85% of the components and materials from this boiler get recycled once it’s reached the end of its life.

Main benefits of the Vaillant ecoTEC exclusive with Green iQ combi:

  • Available flow rate of 17.8 litres per minute
  • ErP rating: A
  • Compact size and dimensions (720mm x 440mm x 474mm)
  • Quiet boiler, operating silently in the background

Energy Efficient Combi Boilers Installed by BT Morgan Heating Engineers

With over 35 years experience in the industry, our expert engineers provide a professional and reliable service unmatched in quality.

Whether it’s boiler installations or a power flush to clear out your system, we take pride in the work we do. Everything we can to ensure our customers are happy with every result. At BT Morgan Heating Engineers, benefits we can provide include:

  • Personalised care and attention before, during and after installation
  • No overheads like with larger companies, quotes for same boilers can come at a lower cost.
  • In the event of a breakdown or service, an engineer or technician from the manufacturer can be at your property within a day or two.

For more information on the different fuel types available for your next boiler, you can also take a look at some of our other articles:

For a FREE, no-obligation quote, click here.