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What is a Condensing Boiler – Everything You Need to Know

An image of modern condensing boiler

Condensing boilers are becoming more and more popular around the world. They are slowly but surely replacing the conventional boiler options. According to estimations, around 16% of the global CO2 emissions per year come from non-condensing boilers. Quite the figure, right? It’s no wonder that many countries are imposing specific regulations for boiler usage. More and more of the consumers worldwide start to wonder what is a condensing boiler and how does it work.

What Condensing Boiler is Exactly?

Condensing boilers are the more efficient budget and eco-friendly choice. They make better use of the heat they generate, saving energy, money, and producing fewer CO2 emissions. Modern condensing boilers are considered at least 90% energy efficient, rising to up to 97% for the very best models on the market. Since 2015, the United Kingdom has implemented a series of condensing boiler regulations. Essentially, all new boilers installed in properties nowadays must be condensing ones.

How Does it Work

Condensing boilers generate heat by burning fuel, such as gas or oil. The produced heat is input into a primary heat exchanger and then used by your radiators. Condensing boilers, however, have something which traditional boilers lack – a secondary heat exchanger or “condensing area”. 

They recycle the burned heat from flue gasses. It travels to the secondary condensing area, where the warm air condenses create water vapour. This vapour then turns into water and drains from the boiler. With conventional boilers, the ErP efficiency is lower, since the exhaust escapes out the flue, resulting in loss of potential heat and energy. Remember that you will need a gas safe certificate to have such appliances in your home.

Advantages and Disadvantages

The advantages of using condensing boilers are obvious

  • They are eco-friendly – nowadays, societies worldwide become more and more aware of the negative effects urbanisation and industrialisation have on the environment. Condensing boilers produce less CO2 emissions and thus, are the greener choice we should all consider.
  • They are energy-efficient and budget-friendly – according to most researches, they could save you at least £200-£300 in energy bills yearly.
  • They are modern – because of their undeniable advantages, condensing boilers are becoming more popular. The demand is increasing, and there is now a variety of different brands, styles, and sizes to choose from. This makes it easier to select the most appropriate boiler for your household’s needs. Those boilers are made in line with the latest technology on the market. 
  • They are safer – Condensing boilers are perfectly sealed for heat insulation, and capture air directly from the outside of the room they are placed in, eliminating the risk of anything being sucked into the boiler. There is also no risk of getting in contact with toxic substances, as the condensed liquid is disposed of via a pipe connected to the drainage system.

Condensing boilers do have a couple of disadvantages too

  • They have complex systems – rarely, condensing boilers may shut down in icy weather, as the external pipe is prone to freezing. They may also become corroded by the acidic condensate.
  • They might be a bit more expensive to maintain – this is not true in all cases, and nowadays, with their popularity increasing, condensing boilers are becoming less and less expensive. Even if they are more costly in the store, their extreme energy efficiency definitely makes them the more affordable option in the long run.

Overall, the positives outweigh the negatives, and many experts recommend condensing boilers over conventional because of their energy efficiency ratings.

Condensing Boiler Cost

The cost of condensing boilers can vary depending on the brand, size, style, and complexity of installation. They may be a tad more costly at first, but, as we’ve mentioned a couple of times, condensing boilers are really worth it in the long run. The cost of a new condensing boiler may be anywhere between £400 and £1600. 

You can get a package deal and hire a company that will be able to both supply the new boiler and install it. A reliable service provider can send a Gas Safe-registered pro to take care of your boiler installation in London. The cost of the fitting service depends on the complexity of the task.

Condensing Boiler vs Combi

So, what is the difference between a condensing boiler and a combi boiler? Combi boilers combine water heating with a central heating system. They are small and compact, occupying less space in your home. Combi boilers could also be condensing ones if you add a Flue Gas Heat Recovery System (FGHRS). It uses the heat inside the waste flue, coming from the burning of gas in your heater. The heat is then used to warm the cold water in your boiler. The process lowers the amount of energy needed, so FGHRS could make all gas combi boilers up to 99% more efficient.


Condensing boilers are the future. Their most essential benefits are:

  • Energy-efficient and safe
  • Cost-effective
  • Reduced carbon footprint
  • Modern and up-to-date with the latest technology in the industry

Now is an excellent time to consider replacing your old boiler with a condensing one, especially if it is no longer functioning properly or if it is hurting your budget. It’s best if you hire a professional, who will be able to check your property layout, size, etc. and advise you about the most appropriate boiler for your needs.

What is a Condensing Boiler – Everything You Need to Know

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