Condensing Oil Boiler

What do I do if my boiler is more than 15 years old?

Typically, the “as new” efficiency of an oil or gas boiler over 15 years old would have been less than 80%. Its present efficiency today, due to wear and tear is unlikely to be greater than 70%.

The current range of boilers available today will have efficiencies greater than 90%. This represents an operational improvement in efficiency of up to 20 percentage points

Increasing the operational efficiency of your boiler by this amount represents an actual fuel saving of more than 25%.  In other words, by replacing an older, low efficiency boiler with a new, high efficiency boiler, you can cut your fuel bills by a quarter.


So, replacing old boilers makes good sense for three reasons:

  1. Significant fuel cost savings with can only increase as energy prices escalate.
  2. Improved reliability and safety.
  3. And now, with the Better Energy Homes scheme, you could even get a grant to help cover the cost of boiler and heating control upgrades.

If you have a boiler older than 15 years then it is most likely during the next few years that you will have to replace it on reliability grounds in any case. Change it now and start saving immediately!

By planning the change (rather than it being forced on you in the depth of winter when it breaks down) you can get competitive quotations and reduce the cost.

Hint: Remember, replacement costs are lower in summer Oil, Gas, what’s the best type of replacement boiler for me?

When replacing a boiler, the first consideration should be about which fuel to use. Generally, you should consider replacing your boiler with one that uses the same fuel. If you have a natural gas supply then it is likely to be the lowest cost option in terms of both boiler installation cost and running cost. If you don’t have a natural gas supply then the choice is between oil, LPG or pellet boilers. For rural areas or areas that are off the national gas grid, oil or LPG are viable solutions.


Should I install a condensing boiler?

Where possible, you should consider installing the highest efficiency boiler possible.  Condensing boilers have a much higher efficiency than non-condensing boilers, however there are some rare situations where installing one may not always be feasible.

Since March 31st 2008 when installing a replacement oil or gas boiler it is now a requirement that the boiler be condensing, where practical (Section L3, Building Regulations Part L amendment – S.I. No. 847 of 2007:-

A guide to assess specific situations where the provision of condensing boilers is not practicable can be downloaded here: Condensing boiler installation for existing dwellings.pdf (size 353.4 KB)


What’s a condensing boiler and how does it work?

Condensing boilers are highly efficient. They use less fuel and have lower running costs than other boilers. Higher efficiency levels are made possible by extracting heat contained in the combustion gases, which would otherwise have been lost to the atmosphere.

This is because both oil and gas contain hydrogen locked within their chemical structure. When oil or gas is burned, the hydrogen links with oxygen in the air to form H2O (water). This water (as vapour) can be seen from the exhausts of cars on cold days. The vapour (or steam) contains about 8% of the total fuel’s energy and capturing it makes energy efficiency sense. This is exactly what condensing boilers do. They “condense” the vapour and capture the energy contained there, making modern boilers so much more efficient.

The SEAI HARP (Home-heating Appliance Register of Performance) database maintains a list of all oil and gas boilers, and their efficiency, that are available on the Irish market. This list is available on their website at


Heat Serve install only Grant oil boilers, the No. 1 preforming oil boiler on the HARP database.


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